Doflamingo stomps, hard. The most we have to suggest that Ace can handle Admiral tier threats was him clashing with Aokiji, which doesn't mean much when he had an elemental advantage. Doflamingo isn't Admiral tier either, though him breaking out of Kuzan's ice is a more impressive feat, plus without his DF powers, Ace got wrecked by Teach.
We also don't know how much stronger Ace got after facing Jimbei, other than that it was by some fair extent. However, considering Gear 2nd Luffy was able to equal Jimbei, I find it highly doubtful Ace is much stronger, if at all, than Part 2 G3 Luffy. That being said, the most difficulty Ace could provide to Doffy is maybe making him use his Awakening, at which point it becomes an absolute slaughter.