Xen (or any emulation virtualization technology)
Pro: Difficult to overcommit memory
Con: Requires more memory

Linux-VServers (or any OS-level virtualization technology)
Pro: Requires less memory
Con: Trivial to overcommit memory

One interesting aspect of this one though is that it benchmarks filesystem with noatime on and off:

• Serverwide Performance Benchmarking

The conclusion is that noatime doesn’t improve performance under the set of benchmarks used which are meant to be representative of a website with a database backend.

It looks like IE 7 has really poor string performance in JavaScript when benchmarked with Apple’s SunSpider benchmark. Of course Apple’s benchmark shows Safari beating Firefox 2 and IE 7. I’m not sure I have the time to investigate the fariness of the benchmark. Sure would be nice to have an independent JavaScript benchmark. I’m also curious as to how Firefox 3 would do in comparison.

• The Great Browser JavaScript Showdown