I compared Mac OS X to Ubuntu 12.04 running as dual-boot on the same hardware, as a VirtualBox guest running on Mac OS X host, and as VMWare guest running on MacOS X host.
Results were repeated over multiple runs, and on every run (not just average of multiple runs) Ubuntu came out on top.
Do remember to sort results by 'Name' column, and then compare the scores.
The software I was using has only 32-bit tests in the free version, and they charged money for 64-bit tests. So these benchmarks are only 32-bit. In any case, still Ubuntu won hands down on Apple's hardware!
So much for 'Walled Garden' experience being better :)