I think people are thinking about the workrate that Jonas has and about the fact that he's defending a lot as well as he carries the ball forward.
Marveaux, from what I've heard so far, is more an out and out attacking midfielder that probably isn't that suited to make his PL debut against one of the best sides in the league.
Agreed, say we were to play a mid-table/newly promoted team as the first game of the season, I would probably start Marveaux then. We shall see like.