I have both types of finishes, and have found the satin nickel to be more durable than polycoat, but that's almost damning with faint praise, as the polycoat is very good. (It'll take a beating that a blued finish couldn't handle.)
The only disadvantage of the polycoat finish is that when its really banged up, its hard to get it looking good again. (One Forum member here, however, has found a fix, but I don't remember what it was.)
Avoid Hoppe's on the nickel finishes. Most nickel finishes have a copper undercoat, and micro-cracks in the nickel finish will let the Hoppes and other solvents that go after copper get under the nickel and eat away the copper base. THen the nickel starts to flake away.
Avoid anything with acetone on Polycoat (Gunscrubber, brake cleaner, carb cleaner, Ed's Red in the original formula). In the newest Polycoat finishes, the worst that can happen is that the finish might be dulled a little, but in some of the older finishes, it can really make it look bad.
(I tried removing polycoat on a pre-B made in 85, and literally soaked/immersed it in brake cleaner, and it just dulled the finish. It took automotive paint remover to get the finish off.)