When comparing Unreal Engine 4 vs O3DE (previously Lumberyard), the Slant community recommends Unreal Engine 4 for most people. In the question“What are the best 3D game engines?” Unreal Engine 4 is ranked 2nd while O3DE (previously Lumberyard) is ranked 14th. The most important reason people chose Unreal Engine 4 is:
Blueprints are authoring tools designed for non programmers so designers and other team members can help tweak and prototype. UE4's Blueprint scripts resemble flowcharts where each box represents a function or value, with connections between them representing program flow. This provides a better at-a-glance indication of game logic than a simple list of events, and makes complex behaviors easier to accomplish and games a lot faster to prototype.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro A visual scripting system for non-coders enables quick prototyping
Blueprints are authoring tools designed for non programmers so designers and other team members can help tweak and prototype. UE4's Blueprint scripts resemble flowcharts where each box represents a function or value, with connections between them representing program flow. This provides a better at-a-glance indication of game logic than a simple list of events, and makes complex behaviors easier to accomplish and games a lot faster to prototype.
Pro Lots of resources to learn from
Epic provides multiple official video tutorials, lots of free example projects and content, an extensive wiki and regular streams showing how to use latest features.
Pro Powerful material/shader system
Allows a texture/material artist or VFX artist to create amazing effects from the ground up.

Pro Free development license, including source code
The engine, including full access to source code, is free to use; a 5% royalty is due only when you monetize your game or other interactive off-the-shelf product and your gross revenues from that product exceed $1,000,000 USD.
Pro Realistic graphics
Pro Developers have full control of the engine and source code
UE4 gives full access to the C++ source code allowing editing and upgrading anything in the system.
Pro Dynamic global illumination with voxel cone tracing decreases the computational power needed
Voxel cone tracing is a similar algorithm to ray tracing, but uses thick rays instead of pixel thin rays to be able vastly decrease the amount of computational power needed.
Pro Easy to use animation blueprints
Unreal Engine 4 is one of the best game engines. It is super easy. It dosent require any use of coding due to Animation Blueprints
Pro Spectacular lighting visuals
Pro Cross-platform editor and export
This engine exports for a big range of platforms including Linux. The editor can be run on Windows, MacOS, and Linux (Early Access).
Pro Active community
Forums have many active and friendly members that are quick to respond and help out. Even staff is very active on forums.
Pro AAA Ready
This is ready to make the next AAA game.
Pro Fast compilation for quick iteration
Recompiling an entire game to test a small change takes up a lot of time. UE4 quickly compiles in seconds instead of minutes improving iteration time by an order of magnitude.
Pro Quick release-cycle
New feature releases can be commonly expected about once a month.
Pro Professional feature set for all aspects of game development
Almost everything a game developer wants has a deep and sophisticated tool waiting for them in UE4. No external plugins are needed to make powerful materials, FX, terrain, cinematics, gameplay logic, AI, animation graphs, post process effects, lighting etc.
Pro Proven track record
Pro No coding experience needed
Pro No royalty charges and completely free
Pro Amazon has announced 3 in house games using it developed from Amazon Game Studios
As a proof of how much Amazon is committed to the project.
Pro Advanced VR support and VR Samples to bootstrap your project
Advenced stereoscopic reprojection to save rendering time.
Pro Landscape editor
Sculpting and painting tools for terrain and instanced details.
Procedural generation of terrain.
Pro Roads and Rivers tool
Built-in support for roads and rivers to ease the design of rich game environments.
Pro Free development license, including source code
Full source code for Engine Editor and every tool.
Pro Easy to create full realistic natural environments
Thanks to built-in terrain, time of day, ocean and volumetric fog systems. There is also a gfx pack with various environmental meshes, cloud, particles, materials and skyboxes.
Pro Very lightweight and scalable entity component system
Multiple entity contexts, reflection, serialization, replication, script binding, event bus (EBus) messaging, fully cascading prefabs (slices).
Every reflected property can be fully exposed in the editor with a customizable gui control and can be animated in the built in animation tools.
Pro Cloud gems
Online oriented plugins composed by both client, server and administration components to easily add various online capabilities without further work (es leaderboards, login, message of the day, downloadable contents).
Since version 1.7 they has been released at a steady rate.
Pro In-editor 3D modeling tool for fast level prototyping
Very advanced 3D prototyping tool with many modeling features and UV mapping support available. If you want you can build any kind of fully textured static mesh without relying on external tools.
Pro Total Illumination v2 Realtime GIobal Illumination
Realistic looking lighting bounces.
It doesn't require long offline precomputation times like other static and dynamic GI solutions based on lightmaps or other similar techniques.
Pro Uses AWS cloud
Other than common aws functionality it supports game specific Game Lift for autoscaling game servers.
Pro Slices a very powerful nested prefab system with hierarchical property inheritance
Modular workflow and flexible cascaded propagation of changes.
Pro Modular system
To easy add and remove modular functionalities to a project and easy share them.
Modules are called Gems and can contain code and/or assets.
Pro Very Flexible Base Shader with many built in techniques
Tessellation and Displacement.
Various Parallax Mapping techniques(POM siluette).
Translucency and Sub surface scattering.
Detail Mapping.
Material Blending.
Emission.
Advanced uv transformation and animation.
Pro Rendering of volumetric fx with full light and shadows support
Global environmental volumetric fog and/or hand placed custom shaped volumes with featuring full lighting and shadows.
Pro High quality free assets packs
Amazon made available a selection of triple A quality scenes filled with high quality assets.
Pro Specular reflection antialiasing
Implements the most recent technique available (published in 2017) from Anton Kaplanyan.
Pro Flexible uber shaders with cache and hot reloading
You can modify shaders while testing the game.
Shader files are modular and annotated to setup the material editing gui and filter out mutually exclusive options. All shader permutation are compiled almost instantly from the asset processor and cached for later use.
Pro Built-in Twitch support even by visual scripting
You can create games that react to keywords entered in a designated Twitch channel and let streamers to invite targeted viewers into their game sessions on demand with ease.
Pro WWise LTX Audio
It is still possible to use the non LTX version with few changes.
Pro Lua scripting with the built-in IDE
Built-in Lua editor with remote debugger to debug Lua scripts running in any device.
Pro Virtual file system with live reload on any device
Optimized versions of assets can be streamed live to any device connected over the network.
This makes possible to implement asset types that hot reloads reducing drastically the time to test new content and little changes on device.
Pro Every aspect of the engine is made with scalability in mind
Multiple grain of control over any kind of engine setting and various kind of Lod systems. Settings can be grouped and applied in batch.
Pro Is the first engine to feature SpeedTree 8
Pro Perforce versioning system pre-integrated with the tools
Perforce also comes with a free version for a limited number of team members.
Pro Cutting edge character shaders
Has skin shaders with subsurface scattering and weighted wrinkle maps, eye shaders with refraction parallax, hair with anysotropic specular reflections, etc.
Pro Order independent transparencies
A must for problematic things like hair , vegetation and scenes with complex solid transparent objects(es glass of water with ice cubes).
Pro Implements the state of the art for Temporal Antialiasing from NVIDIA Research
Special iteration of Temporal AA to battle the ghosting issue omnipresent in engines using other Temporal AA techniques.
Pro New Fbx Importer adds support for every software exporting in fbx
It now works for both static models and animations and support advanced setups(es lods and physics).
Pro Full HDR renderer path with output support for HDR tv standards
Updated renderer pipeline to leverage the full spectrum of precision, luminosity and image processing features of the latest HDR tv.
Pro Cinematic multitrack tool with full featured animation editing
Animation Spline editor supporting huge range of keyframing and tangent editing tools.
Pro Advanced in-game UI with 2D and 3D placing
The UI uses the entity component system so it's fully modular and easily expandable. The UI is easily skinnable and supports border scaling images (scale 9). Powerful layouting system supporting multiple screen resolutions. Being based on the entity system every property can be fully animated.
It is elegantly managed in a separate entity context so it doesn't get messed up with other kind of entities and their components like in other engines, but it's fully decoupled communicating with entities in other context on specific event buses.
Pro Full source code repository with updated development branch now on GitHub
See here.
Cons
Con Very high build size
A blank project will build in to a minimum of 200 MB.
Con Slow
Compared to other engines, UE4 seems to perform various actions considerably slower. Actions like starting the engine, opening the editor, opening a project, rebuilding shaders, updating references, calculating lightmaps, saving projects, etc take long enough to get irritating and end up wasting precious development time.
Con Extremely long build times
Making a full rebuild, including engine can take a good 30minutes. If you plan to use Unreal professionally, you better get some licenses for Incredibuild as well.
Con Hard engine for beginners
This engine not easy for beginners
Con Steep learning curve
Especially when compared to its primary competitor, Unity.
Con No drawcall batching, performance is very bad on mobile
There's no dynamic batching support to minimize drawcalls. There's InstancedStaticmesh concept in UE4, but it's 3d only, functionally limited and requires hardware support which rules out most mobile devices.
Con C++ - oriented development cycle: slow turn-around times
The Unreal Editor is the main place to do stuff (of course), so if someone wants to do a lot of C++ stuff, the compilation and linking turn-around times can be painful. Still they probably are quite fast in comparison to the provided featureset.. Still ,they are far from optimal.
Con Poor documentation
Most of the "documentation" for code is actually just automatically generated from the source. If you're interested in knowing how things are supposed to work, you must either go to their answers site or pay for UDN.
Often their examples won't even compile, since they were written for now outdated versions.
Con Royalty based
5% of profits will go to Unreal after $3000 earned in a quarter.
Con They spend more time adding features than fixing existing ones
Con C# not natively supported
UE4 does not support C# natively, but this can be achieved through MonoUE, although it requires using the MonoUE fork instead of UE itself.
Con Poor source control support
Merge tool is not working.
Con Poor quality assurance on their releases
After each release they almost immediately release a hotfix. And another one. And another one.
Con Unreal Engine crashes a lot if you don't have the required system requirements
Con Sparse Resources for C++
C++ happens to be the main suite for Unreal, yet the documentation is very, very sparse.
Con Extremely poorly designed
The code is a mess.
Everything is connected, a single Actor is 1500 bytes, because it contains a million things that Epic once needed in a game.
Inheritance for AActor: AActor > UObject > UObjectBaseUtility > UObjectBase
Con Difficult for Mac users
If you're installing it on Mac, you simply download Epic games launcher and watch it download nothing endlessly.
Con Tutorials do not go in-depth enough
The blueprint tutorial just teaches how to turn on a light when you press f.
Con Proprietary
Con Not available on Linux
Con No Terrain Editor included
Con Bad support
The epic games team only assists with billing and account issues, not bugs.
Con Terrible physics

Con Frequent crashes
Often the editor crashes interrupting your work.
Con Poor error messages
Con Rarely works
Con Some Legacy systems are still incompatible or not fit well with the new entity component system
At first it is common to try a feature and then understand that it is meant to work with the legacy system and not with the newest one.
Legacy systems get replaced or updated to work well with the new entity component system in every new version, but there is still some work to do.
One example for all Flow Graph visual scripting is meant for the legacy entity and Script Canvas is the visual scripting conterpart for the new entity system, but it is still not available at the moment.
Con No source code repository with updated development branch (requests for Github support currently pending)
You need to wait up to 30 or 60 days for fixes as they are shipped with the next official release.
There is no comfortable way to submit fixes and changes to the engine as the forum is the only tool for sharing code.
Con CryEngine with AWS plugins
