I haven't seen Wayans in anything else so I can't speak to him outside of New Girl. Same with Morris. But based on what they have done with their respective characters I think Morris has way more talent. It amazes me that he can pull off such an interesting albeit under-utilized character as Winston. He sells the shit out of Winston's insanity.

Coach is not particularly interesting as written and while Morris fills in Winston's gaps Wayans doesn't do much to infuse Coach with anything distinctive or interesting. He's like male CeeCee. He's had some funny moments but there's no way in hell if the roles were reversed he could pull off a Winston whereas Morris, despite not looking like much of a coach, could do more than Wayans with the little he's given.