If you're looking for a guy that you can line up in the slot, occasionally at RB, and return kicks, McCluster is your guy.
If you're looking for a guy that can carry the ball 20 times a game and catch a pass or two out of the backfield, and maybe make a cameo appearance at FB, Dixon is your guy.
It's really apples and oranges to compare the two- if there was an all-purpose position, McCluster would be listed at that, but since there's not, he has to be listed as either a RB or a WR. I think the NFL should start listing guys like Reggie Bush, Percy Harvin, and McCluster as such. I know I would if I were them.