The purists amongst us will always say Mac, but in truth $ for $ PC’s are cheaper and much more upgradeable. A new mac-book air in the UK costs around £1000! Yet you can build a liquid cooled monster PC for that. Windows 7 x64 is very stable thankfully. I have owned a mac, and a many PC’s and I will always go to PC’s now. Of course you have to take your DAW in to account as well, I run Cubase 6.5 and have never had any crashes or lock-ups even before I upgraded to 6.5, this is on a custom built system too.