Arshes has pretty much answered your question here;
Originally Posted by Vay
if you don't plan to use an external monitor, than go for the biggest screen size for your money;
painter 12 for mac is, sadly, inferior to windows version (no 64 bit support; various screen artifacts probably due to ati cards in current macbooks (I'm blaming corel's fucked up coding though); slow UI;
2 GB of ram that p. 12 works with are getting filled up quite quickly if you're working with print-size documents;
overall, I've had better experience with painter IX.5 and X on mac, those are working better than their windows counterparts;
with 12, I'm quite disappointed — I'd probably doubt switching to mac if painter was the only tool I was working with.
however, PS and artrage have been performing better for me on mac;
also, mac os wacom drivers are better coded.
on the fourth day of glitchmas my painter™ gave to me
four random crashes, three broken brushes, two system hangups & one corrupted workspace