Registry Errors

I posted this in another MB yesterday. Having received no replies, I post it here. This is not of earth-shaking consequences, but inquiring minds want to know.

I have downloaded Registry Mechanic and it runs on start-up. Starting up yesterday it showed no errors, but I ran Norton SystemWorks right afterwards and it disclosed 8 errors. How does Norton find more errors than Registry Mechanic? Is Registry Mechanic any good?