Phoronix has lots of interesting stuff on their site; but before you go through their site in general, check out their benchmark test comparisons between Apple's new Snow Leopard OS, Ubuntu 9.04, and Ubuntu 9.10(alpha)

http://www.phoronix.com/scan.php?page=article&item=ubuntu_karmic_leopard...

And this is their benchmark for Java performance between Vista and Ubuntu

http://www.phoronix.com/scan.php?page=article&item=java_vm_performance&n...

And this is a link to a direct benchmark comparison between Ubuntu 9.04 and Vista!