When comparing Stencyl vs CopperCube, the Slant community recommends Stencyl for most people. In the question“What are the best game engines for beginners and non-programmers?” Stencyl is ranked 11th while CopperCube is ranked 17th. The most important reason people chose Stencyl is:
Power users can also write code in Haxe (similar to Actionscript 3) to create their own custom classes and extend the engine.
Specs
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Pros

Pro Haxe scripting available for advanced users
Power users can also write code in Haxe (similar to Actionscript 3) to create their own custom classes and extend the engine.

Pro No coding required, great drag & drop interface
Visual scripting in Stencyl is based on the MIT Scratch project, which was designed to teach programming. Script elements fit together like puzzle pieces, ensuring that data and function types cannot be mismatched.
Pro Cross-Platform
Publish iOS, Android, Flash, Windows and Mac games without code.
Pro It's a NO-CODE Program, you can add logic without code
Pro The original concept for Ghost Song was created using Stencyl
The original concept for Ghost Song was created using Stencyl 3.x
Pro Great performance on every platform
Stencyl exports your games to native code so they have great performance on every platform.
Pro Allows creating 3D apps and games without programming
Pro Good 3D editor
Includes easy to use 3D editor for quickly clicking together 3D games.
Pro Native WebGL support
Can create 3D games as real WebGL apps, running inside websites. Doesn't use a cross compiler, so WebGL apps are small and download quickly.
Pro Good terrain editor
CopperCube includes a terrain editor. Terrain can be drawn with height painting tools directly in the editor, textures can be painted quickly with automatic texture blending into the terrain. There are also tools for placing grass and bushes, and for distributing meshes automatically over the terrain.
Pro Available on Steam
CopperCube is available on Steam It was Greenlit.

Pro Exports to irrlicht
It was also written by the founder of irrlicht, although it is not open source.
Pro Easy to learn and to use
Pro Fast prototyping
You can quickly develop an experimental working model of the product (prototype), because the engine gives you access to a lot of prefabs, plugins and settings. And, you can use the visual programming to speed up the process, even if later you have to write code in order to improve the final product.

Pro Oculus Rift support
Supports both DK2 and DK1.
Cons
Con Not a powerful engine
Should be used for basic games only.

Con Only available via subscription
There should be an option to buy it outright, especially considering it is written by a one man team....this is not exactly an Adobe level enterprise with shareholders, so there is no excuse!
Con Slow release cycle
Con Updated
It needs much to improve for mobile games, it was left in the era of Flash games. In Android you can not even put the native keyboard, you can not access things like native camera, GPS or native text input.
Con Tile system is somewhat inflexible
