I am also interested in the answer to this question.
I bought Adobe Creative Suite 6 Design and Web Premium and was unable to work in Photoshop or Bridge - i got not enough RAM messages. I spent more than a month with Adobe support checking everything they could think of and got nowhere. I uninstalled the suite, and I just downloaded the trial version, but I get the same messages. I am working within Adobe's recommended requirements for this application-- Windows 7, 32 bit operating system with 4 GB of RAM. Someone advised to change to 64-bit operating system, but I think I cannot increase the RAM. Someone else advised that 64 bit operating system causes problems with other programs. So what is the answer? Am I the only person who is unable to use this application?
Photoshop works well on most systems and has problems on some systems - whether Mac or PC. It doesn't really run "better" on either. That (big) choice of platform should be based on other factors.
Note that Photoshop CS6 only works in 64 bit with Mac OSX.
If you work on large images, Photoshop can really use the extra RAM address space a 64 bit OS can provide. If you're wanting to go with Windows and are hoping for some future-proofing you really do probably want to consider the Windows x64 variants.
Windows 7 x64 is mature and quite functional. Windows 8, not actually having been released to the public yet, is pretty new to be considering just yet (though I've tested it thoroughly). Display drivers may not be ready, plus quite a bit of stuff you may know and love has actually been removed from it (e.g., the Start button).
Personally I'd suggest going with Windows 7 x64 for the time being - it's what I'm staying with - at least until the dust settles a bit after the Windows 8 release.
As far as application compatibility, do you have specific concerns? Windows 7 x64 runs pretty much any 32 bit application very well indeed. It won't run 16 bit applications (e.g., from 15+ years ago), but if you still absolutely need one of those there is the possibility of running Virtual XP in Windows 7.
Thanks for the detailed answer! However I've also tried win 8 32bit and it works fine with photoshop... also it uses less resources than 7, so if you don't have a very powerful pc it could be a great choice. The start button is not this important, when your system runs faster (especially in boot time).