Let me restate the OP's original question.
32 bit to 64 bit
She may wish to have a simple, direct answer.
Say you have a 64 bit CPU and the right 32 and 64 bit drivers
You have both 32 and 64 bit windows 7
You have 4GB of RAM only.
All the applications programs are 32 bit.
Given that,
Is the a significant, if any, difference with using either version of the OS?