i have to agree that the difference would not be that great, infact i used those types of programs that do look like they are freeing up memory, but it was such a resource hog, that i just un-installed it. it was not worth the effort.
i would just rely on getting more ram , and not try to get a program to free it up, you'll end up with double trouble if you have a memory leak. then you'll just end up with freeze up.