1 500GB drive vs S/W RAID 0 with 2x250GB

[clay]

I'd say it depends what you're going to be using the drive(s) for. If you're doing video work where render times would be helped by a fast array, then go for it. If you're just storing a ton of Word documents or photos or music, then I'd say go for the single disk option. The speedup will be noticeable, but whether it's actually usable in your setup depends on what you're going to be using it for.

good luck