Seth Mitchell is the better prospect, he actually steps up his competition and is starting to fight higher ranked guys.
Being unbeaten means nothing when you look at the level of opposition he has faced. He should be unbeaten because he hasn't faced a single live body yet and he still managed to nearly get himself KOed against a nobody bum in Sconiers. Wilder has no Chin. None. There is a reason he is 20+ fights into his career and is still fighting the dregs of the professional Boxing World in strip club-level fights in Alabama and that reason is his Glass Jaw. He is going to be exposed as soon as he's in with a B or even C-level opponent.
His management will eventually have to relent to public opinion and put him in with a live body and when they do he is going to be savagely KOed.
Forget him and watch Bryant Jennings.