When comparing Loom SDK vs uScript + Unity3D, the Slant community recommends Loom SDK for most people. In the question“What are the best 2D game engines?” Loom SDK is ranked 45th while uScript + Unity3D is ranked 97th. The most important reason people chose Loom SDK is:
Loom can live update changes in realtime, allowing you to see them on multiple devices immediately.
Specs
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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 Automatically generates nodes for third-party script assets
uScript's nodes are a visual representation of actual code blocks, and it takes advantage of C#'s reflection capabilities to automatically create nodes for any scripts it finds in your project, regardless of the source. This makes it inherently compatible with pretty much everything.
Custom nodes can also be created by hand, for cases where the automatically created ones contain more elements than they actually need.

Pro Versatile flow diagram script model
Modeled after UDK's Kismet (the predecessor to UE4's Blueprint), uScript's scripts 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 Generates C# source code
Nodes are translated directly to C# files in your project. This is great for learning to code, and also for advanced users who can use uScript for fast prototyping and then further optimize the scripts if necessary.
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 Not that easy to use
It's a lot more complicated compared to something like Playmaker. Same tasks take a lot more time.
