Some more elaboration:
Modern Hard Chrome finishes like Tripp Research will do for you don't cost much more than the cost difference between a carbon steel and stainless gun. They are EXTREMELY hard and wear resistant, much more so than bare steel (figure maybe a Rockwell C hardness of 30ish for the steel vs. 70-75 for the hard chrome). They provide good corrosion resistance and don't flake or peel off like older nickel finishes would. Alot of people consider hard chrome the best all-around handgun finish, if you don't need a dark colored gun. However, if you need the absolute maximum in rust resistance, it is not the best choice; something like NP3 or electroless nickel would be better in that case. If it has to be black, you are stuck looking at the polymer finishes like Black-T (or bluing, of course).
Stainless steel provides better corrosion resitance than carbon steel, but how much better varies depending on what alloy was used in your gun. It is not as strong as carbon steel generally, though there are exceptions depending on which alloys you are comparing. Modern stainless guns don't have the galling problems that the really early ones did; if the gun was made in the last 20 years by a decent company, it is a non-issue. Stainless steel, like carbon steel, will show wear and scratches alot more easily than hard chrome, because it is much softer. However, with bare stainless steel "re-finishing" just amounts to a re-polish or re-bead-blasting of the bare metal, so it is less of a concern generally. This is only a problem if you are looking at mirror-polished stainless, which will show scratches if you just look at it funny.
