Both are good, but they aren't miracle workers either. They have their limitations. You have to remember that both are actually pretty mild medications. This is obviosuly good for the fish, because then they aren't anywhere as negatively affected as they would be with harsher medications. But, they also don't pack quite the punch to the bacteria or fungus that you are trying to kill that the stronger medicines do.
I think that it is a good idea to have a broad spectrum of medications on hand, because you never know the moment you are going to want to treat your fish. Having Mela-and Pimafix around is good. But also a good anti-ich medication, a good strong set of anti-bacterial medications, and maybe more depending on what your fish seem to get. If you store them away in a cool, dark, dry place those medications can last a very long time. Sure, they have expiration dates on them, but those are designed to make you throw away your old stuff to buy new, not because the medicine has gone bad. Like I said, store them away, and if they are unopened, they are good for at least 4 or 5 years.