You might want to read about the pros and cons of 64-bit software at: http://en.wikipedia.org/wiki/64-bit#Pros_and_cons
Many people have fallen into the trap of believing that 64-bit automatically means faster, and the truth is, this isn't the case for the majority of applications. Whether 64-bit Windows executes 64-bit software faster is not something I'm knowledgeable about.
Software like Defraggler are almost always bottlenecked by the performance of your hard drive, not CPU or memory availability. Having 64-bit software in this case would probably not make much of a difference.
Hope this helps!