here is pretty much the only thing i could find on some quality ram testing, but they didnt use vista which kinda defeats the purpose of DDR3 interfacing, xp from what iv gathered does not support it correctly so this wont be 100% accurate, but will add light to the situation.
Memory DDR2-800
DDR3-1600
Latency CL 3-3-3-5
CL 7-8-7-14
Sandra Mem BW int MB/s 7031
7792
Sandra Mem BW FP MB/s 7038
7017
Sandra Mem Latency ns 71
69
Everest Mem Read MB/s 8034
9615
Everest Mem Latency ns 57.8
56.6
Source:
DDR2 vs DDR3 tested head to head