When you get to the McCartney, Dylan, Springsteen, Wonder plane, it's hard to diminish anything. At that point I think it's really down to "wow" factor, which is what I get from Stevie more than the others (having nothing to do with his blindness, just how exciting and original he was.)
I guess if I had to pick one tangible thing in Stevie's favor over McCartney, I'd credit Stevie Wonder for the fact that when he took singular creative control (versus recording what Motown wrote for him, backed by studio musicians), he went on the best creative run of his career. When Paul McCartney took control (went solo, didn't have Lennon and Harrison adding input), his output got worse.