When comparing Amethyst vs Armory3D, the Slant community recommends Armory3D for most people. In the question“What are the best 3D game engines?” Armory3D is ranked 10th while Amethyst is ranked 26th. The most important reason people chose Armory3D is:
Does everything in the same application. No exporting-importing assets, make a cube, hit run, cube appears, make a character, hit run, the character appears!
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro It's free and open-source
Amethyst is published under the MIT license making it open-source and id offered completely free. This allows anyone to give the tiling window manger a try, which is great.

Pro Recently updated and rewritten in Swift.
The application was written in Objective-C, but was recently updated and completely rewritten in Apple's new native language Swift.

Pro Works with keyboard shortcuts, no mouse needed
As it's designed to work closely to how xmonad, Amethyst uses keyboard shortcuts to control the windows being used, meaning no mouse input is necessary. This can make for a faster way to control windows.
Pro Multi-monitor suppport
Pro Has many common layouts to choose from (fullscreen, floating, row, column, wide, etc)
Pro Can switch between tiling and floating mode
Pro Under active development
Pro Configured via UI
No CONFIG file provides security and will avoid making amethyst crash. Instead configured via simple UI
Pro True tiling means never losing track of windows under a huge pile of others
Pro Runs inside Blender
Does everything in the same application. No exporting-importing assets, make a cube, hit run, cube appears, make a character, hit run, the character appears!
Pro State of the art physically based rendering
Physically based
Cycles material nodes
Voxel-based global illumination
Temporal anti-aliasing
Tessellated displacement
Screen-space raymarching
HDR pipeline
Pro Free and open source
Pro Easy to use
Pro Node based programming and materials support
Pro Lightweight
Pro Export to multiple platforms
Export to all platform that Kha supports.
Pro A good community
Although the is an obvious lake of community help, it is still there if you look on the Armory forum or there discord your sure to find help for any problem you have.
Pro A growing community with more tutorials and documentation.
Although Armory has been a little slow in the development, tutorials on YouTube are being released almost daily and the documentation is also being updated regularly.
Pro No programing experience needed
Cons
Con Can be buggy at times
Con There are more user friendly window managers available
There are certainly more user friendly window managers available for MacOS, such as Divvy or Moom. Amethyst, however, is more powerful and customizable than the more user friendly options available and therefore may be a better choice for a user looking for more advanced capabilities and customization.
Con Lack of documentation
Con Not many developers use it
Armory3d seems to be quite exotic and it should be hard to find developers to help in projects.
Con Still in development
Con Slow development
Focus from the developer has shifted to another project, so development of this has slowed considerably.
Con Good looking but a terrible choice for any serious development
Terrible lack of support and lack of a serious delivery strategy. Multiple breaking changes to the master branches (usually the only branch actually) from the core projects as well as the myriad of dependencies it uses make it a nightmare to have something stable to create with. Might be good for prototyping if you stick to the releases, but stay away if you are planning to create something serious.
