Thor looked really crappy in sparring sessions, but he has height and weight on Eddie Hall, also he seems to be less riddled with injuries and is younger, so he's probably a favorite.
Just in case anybody thinks that Thor would be any good in boxing, just watch this:
He's basically a Bob Sapp. Like a lot of big bodybuilder/weight lifter guys, he just doesn't seem to have the instincts for it. The huge weight he's carrying makes him stiff and awkward. For sure he'd out-scrap a random guy on the street, just based on his sheer size and strength, but a professional? No.