Here's a link to a rather interesting post : Windows Vista SP1 vs XP SP2 performance tests - VR-Zone IT & Lifestyle Forum! As the title suggests the thread involves Vista being benched against XP and it shows that Vista has really improved..

__________________
AMD X2 BLACK EDITION 3.2GHz SAMURAI COOLER::GA-MA790X-DS4 MOBO WITH NOCTUA NC-U6 HEATPIPE COOLING::3GB XMS2 PC6400 RAM:: POWERCOLOR 4870 512MB GDDR5 RAM::160GB BARRACUDA RAID 0::SOUNDBLASTER AUDIGY::SAMSUNG WRITEMASTER DVD-RW/PIONEER DVD::HIPER MODULAR 530W PSU::THERMALTAKE ARMOUR Jr CASE::RAZER COPPERHEAD MOUSE::VISTA HOME PREMIUM SP1