Speaking directly to the 32bit versus 64bit question, regarding sheer performance, browsing is probably the very last task one would need to run at 64bit.

An answer from a Microsoft tech to a question a year ago about the advantage/disadvantage of running the (then) new E9 64bit:

"There is no significant advantage of 64 bit over 32 bit as such, it is just that you may use it on a 64bit platform. However, you will have a slightly safer and better browsing experience running the 64-bit version. As it is, 64-bit Windows is slightly safer overall as there's not as much malware aimed at the 64-bit platform and the 64-bit platform has a tighter architecture security-wise."

The whole E9 versus E10 thing is an entirely different thing - lol. I've been goofing around a bit with E10 64 but am not so excited about it.