Really? Marcus to me will have the exact same problem Joe McElderry had after the show: namely that he's undeniably popular (and more than a little bit fit...) but his voice is just extremely bland. Technically, he can sing brilliantly, but if I was in SyCos A&R department I would be really panicking about how on earth they could fill up a commercially viable album for him. Any of the other four, they would have no problem whatsoever, but Marcus is just far too bland.
If there was any justice, the final three would be Little Mix, Mischa and Amelia. It somewhat astounds me that given her extremely natural stage presence, her eye for style and the way since week fucking one she has just "got it", Mischa isn't the runaway favourite to win this series. I think nevertheless that girl is going to sell a fuckload of albums.