6gb ram in imac late 2007

I just bought the 6gb kit from OWC and installed in my santa rosa imac 7,1. Everything runs fine. But I decided to run a benchmark to see if there was any difference from my 4gb kit. I wasn't really suprised but the 4gb kit from OWC beat the 6gb kit big time. I did the same test with geekbench both 32 and 64bit 5 time with each set of RAM and the 4GB kit won. The memory bandwith was a lot higher with 4GB and the memory performance was better with 4GB. Is this due to the 4GB being dual channel and latency 4 and the 6GB being latency 5 single channel or does the imac just like 4 better than 6 meaning is it not capable of using all 6gb of RAM. I am running snow leopard and all 6GB show up in activity monitor and iFreemem app. Please give me your opinion on this.