Dont buy a 40 gig, buy a 60, or 80 gig. You can play PS2, and PSX games on 60, and 80 gig. I know everbody has there opinion ppl who have a PS3 three will say PS3 is best. And ppl with 360 will say Xbox 360 is best.
If you're buying a system for the future, get the PS3. You can get a 40GB refurb at GameStop for $380. You can probably also get one on eBay. If you are looking for the gaming system of the next couple years, then get the X360.
Get an XBox. They are REALLY cheap nowadays (you could get a good used one for about $100) and can play the now classic XBox games, namely Halo2, KOTOR2, and Fable.