There's a benchmark comparing Solaris to Red Hat at Sun's web site. Solaris 10 features a new TCP/IP stack architecture, project FireEngine. Sunay Tripathi posted some performance data on his blog as well that people might be interested in. He will also be posting details about the new architecture and how it allows Solaris 10 to perform exceptionally well on 1-2 CPU and also scale linearly across large number of CPUs. With the low end x86 platform moving soon to 8 CPU (and AMD's dual core, 8 CPU), scaling is something that can't be ignored anymore.