7800GTX by a lot, something like 40-60% faster depending on the workload. why are you thinking about outdated cards? 8600GT, x1950pro, 3650 are all faster and probably cheeper.
nah, im switching comp with my parents, and they have 7800GTX.. and my friend has 7800GS and said it were better than GTX. If I buy a new one I'd probably buy a 8800..