Here
That includes most information on the differences that i could actually find.
Easty is actually the only one that has given you the most correct answer so far. 64Bit has only shown performance gains in industrial applications. For the simple fact it is optimized for 64bit programmes (which are made specifically, rather than for general things like games that have to be coded 32 and 64bit)
Clayton, i want to see proof that you have seen a performance gain whilst using 64bit. Because as it stands, every single source on the internet says the exact opposite.
There is no reason to go 64bit as of yet, because there are not a lot of 64bit apps that you would use. However driver support is getting increasingly stronger and it will benefit you in the future.So i recommend 64bit anyways
It may not have an advantage over 32bit as of yet, but it doesn't have any negatives either. (please don't say driver support)