Evra would be my choice, slightly ahead of Irwin. He is consistently stunning. He has been our third best player this year imo, closely behind Carrick and Vidic. His understanding down the left when Ronaldo is there is formidable and he has one of the best leaps I have ever seen from a man of his size. He is pure quality and probably one of our greatest ever signings in modern times along with Vida. He is by far the best left back in world football atm, something Irwon never achieved.
I think the main reason why people hold Denis in such high esteem is simply because of his loyalty and devotion to the Utd shirt. He also had a great left peg on him and his free kicks and penalties provided us with an unnatural amount of important goals. Undoubtedly he was a United great , but I do think that Evra will be here for another 5 + Years and that will provide him with a platform to become twice the legend Denis ever was....
So if I had to choose, It would certainly be Paddy E.