Poirier has benefited a ton from the move to 155. By not having to obsess over every last calorie to make weight, he's been able to skill-build, and now he's one of the most well-rounded fighters in the game. That said, Conor's offense is still extremely dangerous. And as far as chins go, Poirier is definitely closer to the Brendan SChaub side of the continuum than the Mark Hunt side. You also have to wonder what sort of psychological advantage Conor would have, having finished Dustin so decisively the first time, as well as the fact that he was able to completely punk/pscyhe Dustin out in a fashion that was probably extremely embarrassing.
Way too many people are selling Conor short because they don't like the guy and he lost his last fight to the best LW in the world who's also a bad style matchup for him. Conor is still a massive puncher(bigger than Holloway) and this fight is better style matchup for him than Khabib. Honestly I'd still make him a slight favorite in this one.
As stated above Dustin has benefited from the additional weight. Conor's power may not be effective against a heavier Poirier. I expect Dustin's activity level against top opposition, confidence and conditioning to give him an advantage. If the Khabib/Poirier bout doesn't materialize a Dustin/Conor rematch would make the most sense. The payday would certainly be a career high for Dustin. The winner gets Khabib.