Jim- lower resolution is probably a misnomer. Salt prints I think can look a little "softer" than platinum. That may be an opinion formed from not having seen enough salt prints.
I should have said that I disagree with the assertion that platinum has a lower resolution than silver gelatin. Frankly, unless you're printing on a highly textured paper or not on paper at all, I don't think there is a print resolution issue regardless of the medium. Your negative is going to have a much greater influence on image sharpness and resolution than is your printing emulsion.