another thing could be to look at the systems they work in. Brady Quinn is constantly throwing to 6-7 different receivers in a game (and not just all backs too!), which indicates that Weis is comfortable with him making reads. The difference between TDs and Ints might help too, although you'd want to weight it to account for the different number of pass attempts. If you did that, I think you'd see Brohm skyrocket on the intelligence meter, and someone like Colt Brennan or Jamarcus Russell fall a little bit.
as for smart QBs, i would put Brohm first and Quinn second