When comparing Loom SDK vs Crafty.js, the Slant community recommends Crafty.js for most people. In the question“What are the best 2D game engines?” Crafty.js is ranked 37th while Loom SDK is ranked 45th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Live reload of code and assets across multiple platforms
Loom can live update changes in realtime, allowing you to see them on multiple devices immediately.
Pro Powerful command line workflow
Loom Turbo ($5/mo) gives access to powerful command line tools. For example, "loom new" to make a new project, "loom run" to run it. Packaging, deploy, and live reload are done automatically for you.
Pro Open source
The Loom runtime and LoomScript compiler are open source, with code available on GitHub, allowing you to have the freedom to fix the bugs and add the features your game needs.
Pro Examples
Loom includes over 30 examples ranging from complete sample games to demos of single features.
Pro Familiar and powerful scripting
Loom's scripting language is immediately familiar if you know JavaScript, ActionScript, TypeScript, C#, or Java. Internally, it uses a proven VM technology with over 10 years of heavy use in games.
Pro Good support
Loom devs are helpful.
Pro Cross-platform
Loom can deploy to Windows, OS X, Linux, iOS, Android (including Nook, Kindle Fire and Ouya). There are also custom port available for WP8, Blackberry and consoles.

Pro Javascript

Pro Eventbinding
Easy to learn, based on Entities and Components, the later being class-like objects that entities inherit.
Pro Modular
Has open function binding systems, allowing easy creation of custom components.
Cons
Con Documentation is lacking
Con No visual tools support
There's no level editor, asset viewer or any other visual tools in Loom SDK. Everything has to go through command line. I think it's fine if you really like typing.
Con No IDE
If you like having some huge GUI akin to Gamemaker, Unreal, Unity, etc, Crafty is not for you.
