Honestly, the disparity in rebounding ability is 0 to none. Both average over 10 boards a game, and are among the league leaders. Although Lee averages about 1 board more than Bosh, I don't think that is a deal breaker as far as ability goes.
The point about the injuries is also a bit flawed. Looking at the amount of DNP's is one thing, but if you look at the kind of injuries Bosh had this year, and last year, it's not like strength or conditioning could have prevented them...He was elbowed in the face and had to have reconstructive surgery...that doesn't necessarily make him fragile. Both players are very durable and will play through pain. Lee missed only one game after dealing with the emotional pain of losing his grandfather, and Bosh played through a broken nose, but eventually was sidelined ONLY because his face required reconstructive surgery. I wouldn't call Bosh fragile, and I wouldn't call Lee immortal. The same easily could have happened to him.
As far as athletic ability, it's no question that Bosh has the edge. He's a better leaper, better shot blocker, and better defender, things this team lacked for the past years with Lee at C (egad).
Same goes for shooting range. Bosh can step out to behind the three point line with ease, and can hit the big shot if called upon.
It's a close call, but Bosh definitely gets the nod.