I'll second Aoxomoxoa's remarks about the Windows version's stability. The other night, I had to load one Win save game three times in a row because it kept crashing. With my very limited play on the Mac side, I haven't seen any such instability, but I heard from someone that the Aspyr code has somehow inherited the late-game deal-breaker crashes that affected the Windows version right out of the gate and has since been patched.
I'm still playing through Bootcamp, though. The patch features and especially my two DLC civ opponents just add too much for me to step backwards--same reason I can't go back and play Civ IV now. Besides, it only takes a minute to reboot...