So really the only main disadvantage of Poirier over Mcgregor is the striking power and skill, however, I don't think Mcgregor was in his best shape at all when he fought Khabib, I'm sure the fight will be a bit closer but Khabib is winning anyhow.
I am hearing all these lame excuses about Conor McGregor not in his best shape when he fought Khabib, no one forced Conor McGregor to fight Khabib as he had more money in his bank account and with is business flourishing there is no point in returning if you are not prepared to take on an undefeated wrestler and he did not back up his big words before the fight and was completely humiliated and now his fans cannot accept the defeat which is cringe worthy 
.The main difference is Dustin Poirier learns with every fight and adjust according to his opponent but Conor just have the same style since i started watching him fight and not much improvement either.
Well, the fight ended and Poirier lost by round 3, Mcgregor survived until mid round 4, as I said, Poirier is simply not a good enough striker to beat Khabib and his takedown defense isn't too good either. At least Mcgregor stopped a few takedowns, Poirier was thrown around like a rag doll.