damn I was about to make the exact same post. OP have you looked into the cost difference? I'm wondering how much I'm going to have to pay to get a hitch installed. I'm leaning towards a hitch, I want loading after a tiring ride to be dead easy, I don't need to haul more than two bikes. Is 1" receiver enough for AM/DH bikes?
I haven't really priced it out either way, but as far as I can tell it's roughly a grand either way when all said and done. My preference would be to go roof, but I have this monster sunroof and I can see why I wouldn't want muddy bikes dripping on there. I'm tall enough that putting the bikes up there post ride isn't an issue though.
Seems the hitch mount has edge in the poll so far. I think I'll look into the price of getting a hitch installed just for comparisons sake.