When comparing Stencyl vs Starling, the Slant community recommends Stencyl for most people. In the question“What are the best 2D game engines?” Stencyl is ranked 11th while Starling is ranked 78th. 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
Ranked in these QuestionsQuestion Ranking
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 Lightweight
Starling is just 12k lines of code and doesn't try to do everything — but what it does, as efficient as possible.
Pro Feathers User Interface Components
With Feathers, you can easily add great user interfaces to your games — or even create business apps with Starling.
Pro Free and open source
Starling is available for free with code available on GitHub.
Pro Strong community support
Forum is always active with knowledgeable developers and with lot of inside info, and post mortems.
Pro Works with Flash
With UI, you can design it in Flash Professional (powerful 2D editor), export to swf file, use GAF convert swf file to gaf file, finnally, load gaf file to Starling. GAF can convert a lot of file swf to one atlas. Alway use same resource in design files (fla) to optimize atlas size, avoid duplicate asset in atlas.
You can use flash to create animation for starling.
Pro Hardware accelerated rendering
Let the GPU do the rendering, the CPU has more important tasks to do.
Pro Cross Platform
It can be exported to web flash player, iOS, Android, Windows, and OS X
Pro Works with AIR's native extensions
Using AIR's native extensions any native code that can be written can be run and used by the game engine.
Pro Constantly updated
New features are added regularly.
Pro Better performance than most alternatives
Starling can run more animated display objects than Unity2D and many others frameworks at 60 fps.
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
Con Poor text/font support
It supports only 4 features for text rendering:
- bitmap font with batching.
1.1. basic distance fields with support for outline and filters via MeshStyle.
1.2 the new multichannel distance field, the ultimate solution for bitmap font rendering. - Draw and upload texture in runtime
So every new text field required texture uploads or vertex/idnex buffer uploads.
skipUnchanchagedFrames keep the backbuffer static for scenes without changes between frames, leveraging a good rendering optimization.
Con Engine supported mainly by one man
Its open source but in most cases community features or pull request are canceled.
