Man to man can still be tough... If your SF cannot defend inside and you play man you are leaving a gaping hole. That's when a 3-2 becomes an acceptable defense against an inside attack.
The only positive to the 2-3 zone in my mind is the extra rebounding. I guess you could also hide a poor outside defending SF, but if you need to run a 2-3 zone to do that, I think you have issues.
Run of the Mill Canadian Manager