IIRC older projects of 3b1b don't necessarily build with later, evolving versions of 3b1b Manim. There might be some mix of versioning questions mixed in with branding questions.
Although the fact that the 3b1b team isn't using the community version makes me wonder why and whether the community version is actually better. In any case I'll take their word for it that it's more beginner friendly.
I believe 3b1b uses his extensive knowledge of the system he developed to sometimes do hacky things that wouldn't be easy to support long-term. His repo may be better for someone who has a similar extensive knowledge, but won't be ideal for someone who is mostly interested in it as a tool and doesn't want to learn its innards.
Community version core dev here, the reason is slightly complicated:
Back in 2019, there was no community edition, and most people based their own work off 3b1b's repository. Back then, Manim used a renderer called Cairo, which was painfully slow especially for 3D Scenes. So in late 2019, 3b1b started work on making Manim use OpenGL as its renderer instead, in a new branch called the "shaders" branch. In mid-2020, the community became frustrated at Grant's lack of interaction with them and slow response in merging PRs, so they decided to start their own fork. However, since the shaders branch was still extremely buggy and unfinished back then, they decided to build off the master branch instead.
In early 2021, the OpenGL transition on 3b1b/manim was "complete" (the shaders branch became the master branch, and 3b1b/manim uses OpenGL as its renderer now). This is probably the main reason 3b1b still uses his own version.
Since we decided to work on the master branch, we were (and still are) using Cairo as the default renderer. However, work quickly began after this to transition the community version to use OpenGL. We currently have an experimental OpenGL renderer, and it actually is nearly as complete as 3b1b/manim. However, since we had to worry about backwards compatibility, tests, documentation, Jupyter, etc., this transition takes a lot of work and is still ongoing. I expect that within 1 or 2 months however, that the community version will become "strictly better" than 3b1b's version, i.e. it can do everything the 3b1b version can with the OpenGL renderer (although it may still be considered experimental).
The reason we recommend using the community version is because it is significantly less buggy, has much more comprehensive documentation, tests, Jupyter support, new features added by contributors and devs, plus if you happen to run into a bug, you're far more likely to have a contributor notice it and make a PR fixing it quickly. Yes our renderer is slower, but we're quickly preparing to transition to OpenGL as a default.
