Poirier has the best overall resume of any current active LW (not counting retired Khabib obviously). Yes, Poirier lost to Khabib but everyone loses to Khabib, Khabib would be favoured & should beat Oliveira too.
Poirier's biggest wins:
McGregor - I agree this win doesn't mean as much as it used to, but I consider it on par with Lee & Ferguson (loser of 3 straight)
Holloway - Max was reigning FW champ & 1 of the top P4P at time of the fight, 13 fight win streak
Alvarez - Alvarez was coming off a win over Gaethje & ranked top 5
Gaethje - top 10 win at the time, looks better as time goes on as Gaethje is consensus top 5 now
Pettis - yes, Pettis was/is past prime, but past prime Pettis also beat Oliveira
Oliveira's biggest wins:
Lee - 1-2 in his last 3 fights prior, or 2-3 in his last 5 fights prior
Ferguson - lost his last 3 fights, I think we can all acknowledge Tony is past prime
Chandler - usually a guy hovering around the top 10 but not really a top 5 guy