Thanks to the increasing popularity of Babylon, it has a growing community of helpful developers. It's easy to find help on their [forum](http://www.html5gamedevs.com/forum/16-babylonjs/).
Ranked in these QuestionsQuestion Ranking
Pro Excellent collision detection system
Impact provides 2 types of collision detection; static and dynamic collisions. Both of which are easily integrated into game development.
Many plugins are available, including one called Impact++ which adds features like pathfinding and dynamic lighting.
Pro Level editor
Built-in map editor with support for tiling, collision layers, and actors.
Pro Extensive documentation available to support development
ImpactJS has an active user community that busily produces tremendous resources including videos, books, tutorials, walkthroughs and more. There are also comprehensive class documentation available.
Pro Truly cross-platform allowing developers to build for anything
Extending the reach of a game developed with ImpactJS is easy due to the cross-platform nature the framework. There are Considerations around performance, resolution and audio, however all can be appropriately addressed when in development. Works in the browser via Canvas, even on mobile. Easily translatable into a packaged app.
Pro Small (but helpful) community
Thanks to the increasing popularity of Babylon, it has a growing community of helpful developers. It's easy to find help on their forum.
Pro A good amount of easy to understand resources to learn from
Babylon provides a playground where you can explore examples and play with the code.
The official documentation offers a wide variety of well-written tutorials on topics from beginner to advanced.
Additionally, there are many tutorials written by the community available that you can find by doing a google search.
Pro great base shader material
Pro Actively developed
Babylon has great project health, with activity on Github daily for bug fixes and new features.
Con Cost of $99
While most HTML5 frameworks are offered as free open source projects, ImpactJS has a one time cost and no free option.
Con Young project
Babylon is quite young compared to many of it's competitors (released in 2013). The community is still somewhat small, however growing quickly.