It's a bit like comparing Bryan Robson and N'Golo Kante. Players from different eras. Robson more of a warrior than Kante and much more of a goal threat, but Kante possibly slightly quicker, more tenacious and schooled in modern tactics.
Irwin's end-product was obviously better, but Evra was better at actually getting forward. He was able to completely dominate the entire flank, both offensively and defensively, more than Irwin ever did (Irwin relied a bit more on his teammates to create the space). It's just that his lack of a final ball meant that all those opportunities often got wasted.
It's bloody close between them. I'm tempted to say Irwin, but the one thing holding me back is that he was mostly doing it during a time that the Premier League was quite a bit behind the other top leagues, whereas Evra was at his peak during the period where it was the strongest in the world.
Evra's greatest attribute over Irwin was his fantastic ball-carrying ability. He'd get us up the pitch in seconds and do it regularly with great energy. The opportunities he created for himself were often wasted though, sadly. Bad crosses were quite normal. But he was very fun to watch, a wonderful player.
Ultimately though, you'd get more out of Irwin's attack, even if he did it 50% less than Evra, because his accuracy was much more dependable. He wasn't one for lung-bursting runs like Pat, but he did time his runs to perfection most of the time. Even now, in legends matches he arrives at the right time to help the winger and his delivery is nearly always great. Super dependable with terrific technique.