When comparing libGDX vs Angel2D, the Slant community recommends libGDX for most people. In the question“What are the best 2D game engines?” libGDX is ranked 14th while Angel2D is ranked 90th. The most important reason people chose libGDX is:
Lots of references, tutorials and open source code to learn from.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Lots of resources to learn from
Lots of references, tutorials and open source code to learn from.

Pro Great performance across devices
While it may not always have the best performance for a particular device or system, it's one of the few engines which consistently performs very well across different platforms.
Pro Fantastic UI toolkit (scene2d)
scene2d is a 2D scene graph, scene2d.ui is a UI toolkit on top of that. It enables very complex mobile and desktop UIs.
Pro Can use any JVM language
Since it's built with Java and runs on the JVM, any language that compiles to Java bytecode can be used to develop games with libGDX.

Pro Uses Box2D
A Java port of the Box2D physics engine is included in libGDX.

Pro Allows you to migrate from 2D to 3D within same framework
LibGDX supports both 2D and 3D game development. Allowing developers to migrate from 2D to 3D with ease without having to switch the engine they are using or having to learn a new API.
Pro Doesn't force a specific design
Unlike some engines, which only allow you to make your game in a few specific ways, libGDX allows you to design any type of game you wish as it is extremely customisable.

Pro Active and helpful community
The libGDX community, in the official libGDX forum is extremely helpful and approachable for any kind of question regardless of the its quality or difficulty.
The forums themselves are a very helpful resource for any issue or guide simply by searching past posts in there.
In addition to the forums, there's also the official #libgdx IRC channel on Freenode.
Pro Interfacing with platform specific code
Sometimes it is necessary to access platform specific APIs, e.g., adding advertisement services or leaderboard functionality provided by frameworks.
Pro Free, open source & permissive license
libGDX uses the Apache License 2.0.
Not only is libGDX free and open source but also it's license gives you a lot of power over the engine. As long as you provide a copy of the license, give credit, do not hold devs liable and do not use libGDX logo in any engine forks you can do pretty much anything you want.
Pro Kotlin support
It is written in Java so you can easily make games using Kotlin and Ktx project will help you get all advantages of this language.
Pro Very easy to customize
Pro Constantly improved
LibGDX itself is pretty mature, and get updates not quite frequently, but various libraries for it are actively updated.
Pro Across platform support
You can write once and run anywhere (Android, IOS, Desktop, Browser) also lately came with lib to deal with VR.
Pro Support for 3rd party tools
libGDX has built in support for many 3rd party tools, including (but not limited to) Bullet Physics, Box2DLights and the well-praised Tiled Map Editor.
Pro Lots of tutorials to get you going
Even though the official documentation might be lacking, there are many tutorials on YouTube for libGDX.
Pro Excellent font rendering support
Very good tools for rendering fonts.
Pro Similar to the Microsoft XNA framework
Old XNA users may like libGDX since it's API is actually very similar to XNA's.
Pro Focusing on object pool patterns, to control memory without pointers
Unlike Unity or other engine, it allows to optimize a language that uses garbage collector when using patterns of objects you can control the use of memory without needing a language like C / C ++, getting the same speed in a more productive language.
Pro Great for prototyping
The framework is focused on prototyping. It has plenty of features to speed up development. It has a console with a lua interpreter, tuning variables and function calls. GWEN is well supported. Provides a simple interface for Box2D. A simple messaging system with which entities can subscribe to to receive messsages among other things.
Pro Permissive licence and easy to extend
Angel2D is built with the idea that you the game developer should have control over the framework and be able to add features if you like. So the code is BSD-licenced and very easy to extend for anyone that has completed a basic C++ course or equivalent.
Pro Great performance
While Angel2D isn't the best performing framework out there it's certainly no slog when compared to competition. Simply by the virtue of being native it puts itself ahead of engines like Gamemaker and frameworks like Love2D.
Pro Simple interface to lua scripting
If you're not comfortable with a basic subset of C++ it is not recommended to use this framework. But the Lua scripting platform is very nice for generating actors.
Pro Very helpful and simple project set up for newcomers
Often with game engines they throw you into unfamiliar territory and let you explore for yourself. While this wouldn't be a big issue with Angel2D due to it being a very simple framework it kickstarts your game prototyping.
Pro Focused on providing convenient features
Angel was created with game jams in mind, so it's focused on providing as many convenient features as possible, but in a quickly understandable way.
Pro Cross platform
Angel can create games for Windows, the Mac, most flavors of Linux, and iOS. It uses the native build systems on each platform (Visual Studio, Xcode, Make), so you can be up and running as soon as possible.
Pro Low-level code is easily accessible
Low-level code that Angel wraps is always just an easy click away, ready to be overridden or improved.
Pro Very light wrapping on all of the libraries
A very important point that's often underestimated. This framework is designed to be removed. It's not there to provide a complete engine for you which you will have trouble moving away from. The basic interface to Box2D is very spartan. You're given the simplest of Box2D shapes, not even polygonal fixtures. This limitation (seems to be) there so that the integration with the engine is very low. You never create a physics actor with anything more complicated than an enum describing if it's supposed to be a sphere shape or box shape.
Cons
Con Not starter friendly
Even default applications fail to load in Android. It doesn't have any documentation on errors either.
Con Documentation could be better
Other than a brief installation / getting started overview, libGDX's documentation consists of an official wiki with several incomplete pages, and automated Javadocs. The community recognizes these shortcomings, and new users are encouraged to ask for help.

Con The project slowed down in development
The number of active developers has decreased, many open issues and pull requests.
Con Build system is clunky
LibGDX uses Gradle, which is very demanding of memory and makes IDEs freeze on anything if your computer is not powerful enough.

Con Does not create compiled code
LibGDX runs entirely on Java and does not create executable binaries.
Con A bit difficult to use
This engine is not well put together. Is made from various free modules each with their own peculiarities. At times it feels you need to learn a couple of libraries rather than just one. Is not an engine for beginners as it requires coding. Lots of coding. You need to be intermediate to advanced in Java to develop in LibGDX.
Con No asset pipeline
Unlike XNA/Monogame, Gamemaker or many other similar platforms, Angel2D doesn't have an asset pipeline. The extents of the asset importing is manually loading individual files in code or naming them according to a convention to load a set of them.
Con No longer supported
Hasn't been updated in 2 years.
Con Incomplete documentation
The entire framework is technically documented at http://docs.angel2d.com/ but certain functionality isn't described in there but rather it's just a list of functions. They all have descriptive names and it should be common to run into a feature which isn't given example to in the "Introgame"-project example.
Con Abandoned by developers
Sadly this project has been abandoned by the developer. The main github doesn't see any pull requests fulfilled anymore. There's a debugline draw fix on the github that's rather simple to fix. It is recommended you pull that fork rather than the master branch. Though the simplicity of the framework still makes it a good choice for prototyping.
