When comparing pyglet vs Rainbow, the Slant community recommends pyglet for most people. In the question“What are the best 2D game engines?” pyglet is ranked 43rd while Rainbow is ranked 79th. The most important reason people chose pyglet is:
Since pyglet is so tightly woven with OpenGL it allows the support of drawing in 3D.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro 3D support
Since pyglet is so tightly woven with OpenGL it allows the support of drawing in 3D.
Pro Cross-platform
Works with Windows, Linux, and OS X.
Pro Written in pure Python
A small advantage, but being a core Python developer, it may be the best to stick to the roots and develop with pyglet as it is able to compile using other Python interpreters.
Pro Open source
Distributed under the MIT License.
Pro Written in modern C++, is scriptable in Lua
Pro Cross-platform
With support for Android, iOS, Linux, Mac OS X and Windows.
Pro Optional FMOD audio engine
Pro Supports Spine
Pro Physics
Box2D integrated with Lua bindings.
Cons
Con Small community/popularity
There is a decent amount of documentation and API to go along with pyglet, but in terms of community support there seems to be very little.
Con Not as feature-rich as other engines
Con Small community
Being fairly new on the scene, there aren't much of a community to speak of.