I don't know.....
I think i would at this point, Flacco was a more highly regarded QB with greater physical skills by far.
But we haven't seen either guy play a game yet, Henne could very well be a better player.
I personally liked Flacco coming out of UD, which is not a division one school like Henne's powerhouse Michigan program but still a solid program producing several solid NFL players (Rich Gannon). Then again they had another QB come out a few years ago and he never even made it onto an NFL roster, i think he played for the Eagles for like one pre-season, i forget his name already.
Flacco i think will stick simply because of his size and again physical tools, but i don't know if he'll be better than Henne, not until these guys play games. If i had a gun to my head (which i might since i am sick of hearing how GOD LIKE Chad Henne is) i think i'd take Flacco over Henne. Based solely on how i saw them play in college and what i know of their physical abilities.