I have 3 different Registry Cleaners (Registry Mechanic 6, System Mechanic 4 and Registry Cleaner) and each one of them found different problems with my registry. Which one should I believe?

registry cleaners?

I have downloaded and tried several registry cleaners and they all claim to clean vastly different numbers of entries? One would remove 67 entries while another would remove 255, ect.

Additionally, If I ran a registry cleaner, uninstalled it, reinstalled it, then ran it again, it would find all the same entries again. If I removed them the first time, shouldnt they be go forever?

I guess what I am asking is why is there such a huge discrepancy between how each registry cleaner functions.