The only difference between 32-bit and 64-bit Windows is the amount of memory that can be addressed. 32-bit Windows can address 2 raised to the 32nd power bytes of memory, which is roughly 4 GB. 64-bit Windows can address 2 raised to the 64th power bytes of memory, which is an absurdly large amount of memory that no computer has.
64-bit Windows is not intrinsically faster than 32-bit Windows. However, if you have applications that would benefit from more the 4 GB of RAM, those applications might run faster in a 64-bit computer.
Finally, an application only uses as much RAM as it needs, regardless of how much memory the computer has.