When comparing Source vs Babylon.js, the Slant community recommends Babylon.js for most people. In the question“What are the best 3D game engines?” Babylon.js is ranked 8th while Source is ranked 18th. The most important reason people chose Babylon.js is:
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 Great documentation
Valve's official documentation website is great for newbies. It demonstrates the pros and cons of the engine (and since the website isn't maintained by Valve, but instead the community, the pros and cons are largely unbiased). There are also a number of pages dedicated to entities used within official Valve games and also community-made mods that were turned into full-fledged games by Valve. These pages explain the ins and outs of how most source programming works. There are also guides for Valve's tools which are both included in Source SDK and in any Valve-developed game.
Pro Many basic entities
You don't need to code your own door or ladder etc. You can pretty much use every entity used in Half-Life 2 yourself easily.
Pro Visual logic, no programming
Of course you can program stuff into source but for level design only, source has a really easy input/output system for your level logic (e.g. doors, trigger when player walks into room...).
Pro Runs on every potato pc
Since it has precalculated lighting, this engine is great for low end PCs too.
Pro Has a built-in video capture and editing application
Source includes Source Filmmaker, a video capture and editing application.
Pro Easy way to export or load source models to unity and maps
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Con SDK is outdated and difficult to use
Source SDK has not been updated in ages, and has instead been "re-released" under different names, e.g "Source SDK 2013 Singleplayer".
It's honestly easier to use the version of SDK included with any Source game, namely Portal 2 or DOTA 2, since both have a variant of Source SDK that is more updated than anything you can find in the tools section of Steam.
Con Only for mods
Normally, you can only use the Source Engine to develop "source-mods" (as Steam calls them), however the developer wiki is correct in saying Valve have a proven track-record for finding source-mods and turning them into fully-fledged games, Black Mesa Source is a good example of this, as it began life as a source-mod available for free, however Valve turned it into a fully-fledged and paid game.
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.