When comparing Stencyl vs Leadwerks, 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 Leadwerks is ranked 36th. 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 Very good entity system, did have GUI functions, easy to use terrain editor with vegetation system.
Good API tutoials, workshop elements which can be loaded from steam.

Pro Both Windows and Linux supported
Pro Built-in level editor
Has an acceptable 3D map editor that is easy to use.
Pro Versatile flow diagram script model
Leadwerks's flowgraphs resemble flowcharts where each box represents a function or value, with connections between them representing program flow. This provides a better at-a-glance indication of game logic than a simple list of events, and makes complex behaviors easier to accomplish.
Pro Community forum offers plenty of support
It makes game developing much easier if you have someone backing you up when you run into a bug or other issues, and get replies within hours .
Pro Decently sized library of tutorials for both Lua and C++

Pro Very clean and easy C++ API

Pro Lua scripting support
Pro Reasonably priced
Standard edition of Leadwerks costs 92,99€. Additionally, it often goes on sale on Steam.
Pro C++ scripting support
Pro Terrain editor
The terrain editor allows sculpting, paint, vegetation placement and importing of external maps. Especially the painting is done very well and can lead quickly to very professional looking results.
Pro Easy to use API and scripting language
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 Little to no support
This product relies on community support, although some members are helpful and quite approachable they don't like to share their secrets with people that are new to programming.
The product is sold as a Full featured platform but it seems to more in the Alpha stage of development as a lot of the good aspects where taken out in previous versions.
Con Has a track record of broken promises
Con Forums are poorly run and censored
Con Highly misleading advertising
Con Only prefabs made with the Leadwerks IDE could be used.
The two main problems for me is that C++ is not as easy to use like LUA. The IDE should also support C++. The secons is that only prefabs can be used which are made with the IDE. So you can not easy made a game that can be modded by the user.
Con Weak out-of-the-box AI
The only AI movement function is going in a straight line.
Con Very buggy
Leadworks is a not complete, it's a work in progress. As such many parts of the engine are clunky, especially the level editor.
