Fedora v. Ubuntu: A Performance Look is a benchmark of games and various operations comparing fedora core 6 and 7 and ubuntu 6.10 and 7.04 (stable and unstable version of each main distro). Interesting, however the benchmarks are really close. I think the widest gap is 5 seconds difference in LAME compilation time and maybe 5 FPS running Enemy Territory. Wonder what that says.... Interesting also to see things like boot time differences.
The article also references a 64 vs 32 bit benchmarks article which is an interesting read.