I would lean toward Iaquinta. Simply because the one upper tier guy that Duffy has faced in the UFC, he was smashed up pretty good. Iaquinta has fared much better against the opposition he has faced which on the whole has been superior.
Duffy walked through their common opponent (Mitch Clarke), while Iaquinta lost via somewhat fluke sub in the opening seconds of the second round after nearly finishing Clarke in the first. Iaquinta has to continue to improve his sub defense. Other than that (since he is not Melvin Guillard) which can be fixed, he has really improved a great deal
Would make a good opener for the main card on the upcoming Fox/Long Island event.