To me it is more specific to the individual(s). Bobby Knight made Indiana #1. Fans can be another determiner, and I find Iowa fans often obnoxious and the coach (and Pearl from days gone by), well, I think that is obvious. OSU fans (outside of one game I attend in Columbus in '85 or '86) have always been good company (annoying for sure, but not rude). I hate that we are now losing football to NU, but no disrespect there and basketball still is nothing to care about outside a game or two. I still pull for all Big Ten teams away from the conference with limited exceptions.
Anyway, with all of that, it is still IU and will always be that way for me when we talk basketball.