When comparing Loom SDK vs GDevApp, the Slant community recommends Loom SDK for most people. In the question“What are the best 2D game engines?” Loom SDK is ranked 48th while GDevApp is ranked 84th. 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
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 Quickly add behaviors to objects
Prebuilt behaviors can be added to objects. This is a very efficient way to add a physics engine or make a platformer game.
Lots of behaviors are included, from the most advanced (Physics, platformer, top-down movement) to really simple ones (like the behavior to destroy objects when outside the screen or the one to drag objects with mouse or touch).
Pro Powerful events system to create games without programming
No need for coding using this system which is clear and powerful: events are composed of conditions and actions.
Actions are launched when conditions are fulfilled. This is a very beginner-friendly way of making games and is still efficient for advanced usage, contrary to most other "block"/"drag'n'drop" systems.
Pro Intuitive interface
Pro Based on GDevelop
The entire webapp is based on GDevelop, an open source native game development software available for Windows & Linux, so it benefits from its advanced development.

Pro Can download an archive of the game source
Even though the tool depends on having a server up and running, you can download a copy of your game to run locally, or host somewhere else.
Pro Great UI
Sleek and user-friendly UI.
Pro Can export your game as HTML5 and for Android
Games can be packaged for Android without relying on any third party tool. You can also export your game and download it to host it on your server or let it be hosted on GDevApp.com.
Pro Shallow learning curve
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 Depends on a hosting service
If the website goes down or closes down, you'll no longer be able to develop your games using this system (but you can download a backup of your game from time to time and open it with GDevelop).
Con Cannot deploy native games
For now, games developed with GDevApp can only be deployed for the Web. Android deployment is in the works, but even then, they won't be native since they are built with web technologies.
