Why not do both? Linux or Mac for the machine and if you need to run a specific application, just turn on the emulator. Crossover Mac works superbly if you have an Intel processor in your Mac.
Looking at the 15" MacBook pro, by the I've specced up/down the 2.4Ghz/2.5GHz versions to have equal 250GB/7200 ATA HD and 4GB RAM, I'm left with the benefit of the 2.5GHz version as being the faster processor and 512 instaed of 256MB video ram. This costs £140 ($210) more - is that worth it for essentially running PS4 - my impression is that extra video RAM is more useful for gaming.