DOC: explain how mamba2 and micromamba2 differ

[lucascolley]

Reading the mamba 2.0 changes page in the docs, I understand the general sentiment that mamba and micromamba have become more similar to each other. I also understand from other docs pages that they are still different in that they can be installed differently.

Aside from that, how do they differ? Why might I choose to use one over the other?