When comparing Orx vs Duality, the Slant community recommends Orx for most people. In the question“What are the best 2D game engines?” Orx is ranked 5th while Duality is ranked 30th. The most important reason people chose Orx is:
Powerful config system that makes orx data-driven and provides an easy to use load/save system.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Powerful config system
Powerful config system that makes orx data-driven and provides an easy to use load/save system.
Pro Friendly community
Good friendly development community ready to help each other with tips and advice for setting up and best practices.
Pro Automatic hot-loading of resources
Automatic hot-loading of resources upon modification on disk, shortens drastically iteration times.
Pro High performance
Written in C with high emphasis on memory and CPU efficiency.
Pro Supports desktop and mobile
Supports Windows, Linux, Mac OS X, iOS and Android.
Pro Data configuration
Orx is a Data Driven engine that greatly reduces required code. You can configure object definitions, bodies, cameras, sound, animation, event tracks, etc.

Pro Custom shader support
GLSL code can be added straight into data configuration files and can be applied to any texture: background or objects whivh allows for some amazing effects. All GLSL versions are supported, again by providing the shader language version in your configuration file.
Parameters are supported and values over time for shader animation.
Pro Flexible clock system
Clock system that provides time consistency and allows time stretching + high precision timers
Pro Flexible and simple FX
Color and translation FX are simple to configure and apply to objects.
Pro Good animation engine
Includes a chaining graph & custom animation events for synchronization.
Pro Free and open source
Uses the zlib license. Lets you use Orx for free for any kind of projects, even for commercial ones.
Pro Input controls and binding
All input devices are fully supported: Joysticks, Mouse, Gamepad, Keyboard and Touchscreen. Multiple physical devices and be mapped the same binding.
Pro Excellent results on performance benchmark
Rated the fastest engine in the OpenFL’s BunnyMark since October 2015.
Pro Great audio support
Samples for sound effects, or streams for music. All sounds can be groups via audio buses just like in a typical DAW (Digital Audio Workstation).
All sounds can be spatial relative to the camera.
Pro Viewport scheme allowing multiple views
Camera/viewport scheme allowing multiple views displayed with camera translation, zoom and rotation.
Pro Good render support
Fragment (pixel) shader support, render to texture, MRT, easy composition and custom rendering support.

Pro Easy post-processing/compositing for complex visual effects
Pro Integrated runtime profiler
Integrated runtime profiler (with graphical display) to easily spot which parts of your game need to be optimized.
Pro Collision handling and rigid body physics
Pro Screenshot capture tool
Supports .bmp, .png, .jpg, .tga and .dds
Pro Multi-Threading
Pro Great IDE Support
Out of the box Windows support for:
- Visual Studio
- Codelite
- CodeBlocks
- gmake
Out of the box Mac support for:
- XCode
- Codelite
- gmake
Out of the box Linux support for:
- Codelite
- CodeBlocks
- gmake
Pro Well-supported C++ wrapper
Orx provides a excellent c++ wrapper for object oriented design, called: orx/Scroll. You can, of course, roll your own.

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.
Cons
Con Feature discovery and explanation could be better
Some features are not well explained / highlighted: for example, unless you use the interactive project initialization, you have to go over the tutorials and examples in the wiki to learn that there is an optional C++ layer, Scroll, developed on top of the C API. Similarly, some major information are missing from the website, wiki and Doxygen documention, and are left for the users to discover in source headers and INI template files, or by searching the forum (e.g. the 0,0 coordinate being the center of the screen and not top left, the list of all Orx scalar types and their use, etc).
Con No network support
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
