Windows Vista is visually stunning but I've noticed that even with a brand new cpu it seems very slow. It must take up a ton of memory.
It depends, if you're happy on the current settings on your computer and you believe you don't need a software upgrade in the future, then XP is ok. But I do believe after 5 years you'll be forced to upgrade coz I believe on those time most software will require Windows Vista so that it'll be compatible on your system