I have a 2009 (I think) iMac. I cant install bootcamp due to broken cd drive, but my gaming experience hasnt been that bad. I played, Bioshock 1,2, WoW, LoL, Assasins creed 1,2,brotherhood, mafia 2. All GTA except 4. Arkham asylum and city, mine craft, terraria, bunch of lego games with my brother, civ 5, HOMM 1-5, cs, sims and there are a bunch out there. Id personally choose the new mac pro and install bootcamp on it. I love mac as a whole, but whenever I wanted to play games quick-switching to windows is great.
EDIT: But if gaming is your priority, and youre not a hardcore mac fan, a rigged gaming pc would work better for you.
EDIT: But if gaming is your priority, and youre not a hardcore mac fan, a rigged gaming pc would work better for you.