Just to share that, I'm playing on MacAir (mid 2013). :D
I have all the GP, EP (except IL) & 9 SP. I have a high setting for the game as well. It's extremely lagging whenever I play on a larger lot or there are more than 4 Sims in one household. I would say that, the specs for the MacPro is far better than MacAir if you wish to play any game.
However, why don't you get a real gaming laptop or any Window machine which can handle it better than Mac? I'm planning to get myself a gaming laptop soon.