In my opinion it's always been how big the changes are and what your plans for the future is for whatever project you're working on.
If the changes are big, yes v2r0 would be appropriate. If the changes are small, but you don't plan on doing any more work with this map, v2r0 is still good. However if the changes are small and you do plan on doing more work with it v1r1 is at work.
This is my subjective opinion, I don't even know if it's correct or if there actually is a manual for how to release stuff.
However, I do have one thing to suggest to you. Could you fix the FPS on that map, I get really low FPS on many places and destroys how well I can hook. This is the only map I actually have a FPS problem with in the entire Nexuiz arsenal. Clip, caulk and remove things in a good and appropriate manner. I'm hoping you did a bad job with it otherwise I would have to live with the low FPS
