PC Mark: CPU
Product Score Graph Difference 1GB 3,307 0% 512MB 3,301 0% 256MB 3,321 0%

PC Mark: Memory
Product Score Graph Difference 512MB 3,022 0% 256MB 3,016 0% 1GB 3,007 0%

PC Mark: Graphics
Product Score Graph Difference 512MB 1,986 0% 1GB 1,984 0% 256MB 1,984 0%

PC Mark: Hard Disk
Product Score Graph Difference 1GB 2,346 +1% 512MB 2,320 0% 256MB 2,319 0%

Sandra 2004 SP2- Integer
Product Score Graph Difference 256MB 2,509 0% 512MB 2,490 -1% 1GB 2,472 -1%

Sandra 2004 SP2- Float
Product Score Graph Difference 256MB 2,509 0% 512MB 2,494 -1% 1GB 2,472 -1%

If you go by PC Mark and Sandra scores, you wont see any difference with 256MB, 512MB or 1GB configurations which is why benchmarks alone shouldnt be used to evaluate a system. Lets look at some more synthetic benchmarks like 3D Marks