When comparing Duality vs Oxygine, the Slant community recommends Oxygine for most people. In the question“What are the best 2D game engines?” Oxygine is ranked 18th while Duality is ranked 30th. The most important reason people chose Oxygine is:
Most interesting is ability to build C++ Oxygine application for Web via Emscripten. So you write C++ code and it will compile it to HTML5/JS.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Open source
The full source code is available on GitHub, where the framework is actively developed. All of the editor, core and plugin code is written in C#.

Pro Great editor
Duality includes a powerful visual editing system that can be used for previewing, integrating, editing and testing game content.

Pro Live reload of code and assets

Pro Very extensible
Because both Core and Editor are completely plugin-based, Duality not only incorporates a clean and modular design, but is also very extensible - even if it wasn't Open Source. In fact, most of the standard editing capabilities comes in form of Editor plugins.

Pro Built-in physics and lighting

Pro Friendly to version control systems
It can be configured to serialize all data in a text-based format, which has been structurally optimized for version control systems.

Pro Used in commercial projects
It has been used in a production environment without burning the place to the ground. Supposedly artist-proof editor workflow with an API for tailoring the system to fit your team.
Pro Games can be built as HTML5 applications
Most interesting is ability to build C++ Oxygine application for Web via Emscripten. So you write C++ code and it will compile it to HTML5/JS.
Pro Functionality can be extended with a bunch of available extenions
All of them available publicly at github.
- oxygine-movie for playing Theora movies with alpha channel
- oxygine-sound player for ogg sound/music with streaming
- oxygine-freetype library
- oxygine-billing for in-app-purchases on Android/iOS
- oxygine-spine for playing Spine animations
- oxygine-magicparticles for playing particles made with MagicParticles
Pro Will be familiar to users of ActionScript3/Flash API
If you are familiar with ActionScript3/Flash API, then you will find it easy to begin working in Oxygine. Oxygine is much like Flash in C++, as its Event Handling model is very close to that of ActionScript 3 and SceneGraph.
Pro Easy to use C++ API with optional C++11 features
Oxygine is written in C++. It provides easy to use API, which is designed with "do more with less code" philosophy. It uses a managed scenegraph system that takes care of rendering and updates, and provides ability to extend with custom rendering and updates.
Pro Free, open source and cross-platform
Oxygine is a free framework that works on OS X, Windows, Linux, iOS, Android, HTML5. It's licensed under MIT with source code available on GitHub.
Pro Robust
It's very rare to experience bugs with Oxygine.
Pro Allows playing movies with alpha channel
Using oxygine-movie extension for Oxygine you could play in your game any videos encoded with Theora codec.
You movie could have alpha channel and used as simple sprite instead of classic spreadsheet animations.
Pro Allows for flexible contol over draw processes
Pro Fast
Cons
Con Visual Studio required
To have possibility for scripting you have to download entire Visual Studio and spend 10 GB of free space
Con Requires windows for development
Con Inactive
The project does not seem to be active: there has been no new commit since mid-2019, the Twitter feed for the engine stopped posting news in 2018, and the forum is offline as of May 2021.
Con Little community support
Oxygine is a young framework. It was first released in 2013 and has yet to gather a large community. As of February 2016, the forum had just 123 members.
Con Not many tutorials available
There are not many tutorials available that teach developers on how to make a game with Oxygine from scratch. Because of this, it may be harder to pick it up or to start learning game development by using this engine.
