When comparing Unreal Engine 4 vs Panda3D, 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 Panda3D is ranked 4th. 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
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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 Free, open-source, and permissive license
The liberal license allows use of the engine for any purpose without restrictions or royalties.

Pro Will be very easy for developers already familiar with Python
Although it's possible to use only C++ to program in Panda3D, all its power is available to the Python scripting language, while not trading in performance since the performance-critical parts are implemented in C++.
It has a powerful binding layer that exposes the vast majority of the API via Python-based interfaces.

Pro Supports most popular physics engines
Panda3D has in-depth integration with industry standard physics engines such as Bullet, NVIDIA PhysX and ODE, but also offers a simpler built-in physics engines that will cover more basic needs.

Pro Flexible scene and object hierarchy system
Creating weird world constructs is generally a breeze. The node system the engine runs with allows to build self-looping worlds and, on large scale, non-Euclidean scenes without having to introduce a huge amount of custom code.

Pro Powerful profiling and debugging tools
Panda3D has a suite of powerful tools to help track down performance bottlenecks, memory leaks and examine internal state.

Pro Supports browser deployment
Panda3D offers web plug-ins that allow deployment of an application to all major browsers. A WebGL port is in the works as well.
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 No unified editing program
Unlike Unity and Unreal, Panda3D doesn't currently offer a single, unified editing program in which objects can simply be dragged in and assigned properties (although third-party solutions are available). Developers are expected to design their scenes in a modelling program like Maya or Blender instead, and import them into Panda3D using Python code.
Con Limited tutorial
Step by step tutorial is limited. Manual is too general and short without examples. Samples are too complex for beginners.

Con Direct3D support is behind
Direct3D support not up to par with OpenGL support, only version 9 is supported.
Con Terrible compilers support
Does not support any other compilers then MSVC on Windows, neither Clang nor MinGW.
Con Developer isn't very competent
Panda3D only has one developer and he utterly fails to fix problems with his engine, instead focuses on style guidelines and breaking code.
Con Loading Pandas3d will change your builtins to contain non explicit references to non-standard helper functions
A lot of the pollution comes from storing global state. Instead, you can store and update the global state of a namespace instead. As for the built-in pollution, you can make a wrapper that backs up builtins, imports pandas and then restores builtins, though this may not work as pandas almost certainly uses it's extra builtins to work. The best thing to do would be to explicitly import the same objects that are in the builtins over the top of the modified builtin namespace, although it doesn't remove the code smell, it helps to make things look less (if not at all) magic.
