Haskins is better. That is a fact. Haskins had 533 attempts in 14 games. He carried the offense. Tua had 345 attempts in 15 games. Adjusted for 14 games that would be 322 attempts. That is a world of difference. Haskins simply contributed more to moving the offense and scoring, significantly more!
In addition to that, Haskins has prototypical frame you want, Tua does not.
A smaller guy who does not contribute nearly as much cannot be better. If you are smaller you have to contribute more, be special about something, in performance. And Tua is not. He is not better, on performance.
Finally, on performance, Tua is a bigger risk, he has whacky numbers. His performance is akin to Kellen Moore, Case Keenum, Derek Carr, Brandon Doughty, those types of QBs in last year in college. His performance is not akin to Luck, WIlson, Mahomes, and others who actually translated great to NFL game.
All that boils down to this. You do not suck for a QB like that, not on this year's performance.