I used standalone talos to test a 64-bit Mac OS X build against a 32-bit build. I created the two builds using the same optimized configuration and the same mercurial revision. Since only the 32-bit build can load any of the plugins that ship with Mac OS X 10.6 I removed all plugins from the plugin search paths. This way the 32-bit build wasn’t hurt by having to deal with more plugins than the 64-bit build. The tests were done on Mac OS X 10.6.1.
Ts: 64-bit is 6.5% faster
Tp: 64-bit is 6.3% faster
Twinopen: 64-bit is 5.1% faster
Tjss: 64-bit is 8.7% faster
Tsunspider: basically a tie, 64-bit is 0.2% faster
I’m not sure what all of the factors contributing to these results are yet, but it seems Apple’s investment in optimizing the OS and developer tools for x86_64 paid off.