At the risk of sounding like the rich kid, if you can afford it get an iMac - with the added memory options from purchase. Even with the fully immersive game world that I like to set-up for my FM games (English leagues down to Level 12, top two divisions across major European leagues, Scandinavian, South American leagues, plus Mexican and MLS with the large player database etc) the processing time between matches, while the computer calculates results and events from around the game world, is next to nothing compared to the ordeal I put my old PC laptop through with FM11.
The game rates my computer's graphic processor at the full 5 stars. The matchday animation is as fluid as the programmers intended it to be (although flawed by dodgy AI as addressed in another thread) and I can even put the game into windowed mode and play music and video from iTunes, YouTube, BBC iPlayer etc at the same time without affecting the functionality of either the game or the other media. I can play, say, QI in a window behind the game, and then just drag the game window out of the way if I want to see what they're actually talking about. I sometimes have to turn off the game's sound though, in order to hear the other media clearly.
I spend much more time actually prepping and playing matches now, rather than waiting for the game to roll around from Thursday to Saturday.
On the Mac you have to buy the game through Steam, so all official patches update automatically. You can still access the relevant files to add new kits, badges etc as I have been doing with this edition.