I cannot comment on Flacco since I have never seen him play - I have seen Henne play a lot the last four years - but the argument you are setting up, while typical in sports, is really bogus
it has nothing to do with where they played - it now comes down to their ability to perform in the NFL
there have been great NFL players from small schools and flops from big schools
actually the first pro quarterback that I ever saw playing in college was Kenny Anderson of D3 Augustana and at half time he had led his team to a 3-2 lead over my college's not very good team -
Kenny Anderson played 1971-1986 in the NFL for Cincinnati, started most of those years, and took his team to the Super Bowl and since retirement has coached for the Bengals, Jags, and now the Steelers
and he was a Division III - D3 player - who looked not so very good when I saw him
he would not have been a better player had he played D2 or D1AA or D1A - the fact that he played North Park, Wheaton, Carroll, Carthage, Illinois Wesleyan and Milliken during his college career in the CCIW rather then the SEC or Big 10 and never played against a D1 team meant nothing -
it has to do with the player, not the division of football that they play in it is up to the scouts to see if they can discern NFL ability
Henne - Flacco - it is up to them as individuals, has nothing to do with where they played