OS's haven't gotten faster as they've gone 64bit..the isn't a significant difference in speed between Snow Leopard and Mountain Lion. Just like there was no diffenence between xp 64 and 32 going forward.
Browsers have gotten faster in 64bit that'd be news to me..
The creative suite is a memory hog and and not applicable what where talking about here. Yes PS is faster if you give it more RAM.
In OSX 32bit applications can address 4GB of memory the 2GB limitations is artificial and limited to Windows.
As you can see here, some things get faster (and some slower). But in the end, you have to compare a 32-bit version of an OS with a 64-bit of the same OS.
http://www.iinuu.eu/en/it-guru/windows-7-32-vs-64-bit-performance-benchmark
Then we have Firefox 64-bit being better than 32-bit
http://www.favbrowser.com/firefox-32-bit-x86-vs-firefox-64-bit-x64/