There is a little ongoing debate around here about OSes and RAM. I decided to conduct a little research and find out the answer, at least here on THG. So:
I have over 100 servers in house and have found that a 64-bit Redhat running more than 4GB (most of my machines run 8-32GB RAM) is far superior to the 64-bit win2k3 servers running more than 4GB of RAM.