Thanks Magenta, easy question-hard answer. Up until John's death I would of said Paul. Paul was doing much better in his solo career, still considered a rocker and had put out some really good albums while John seemed to be out of focus. I saw McCartney's first tour (Wings Over America), it was great. But in the years since, Paul has become much more pop oriented while John's legacy has gotten stronger and stronger. I think John's murder made everyone much more aware of his human qualities and the strength of his music-When someone who is singing about peace and love gets killed it makes everything he said resonate much more and become more important. I probably would have preferred John's music more now anyways as I got older and my tastes changed, but his death definitely had an impact on his popularity and the way we look at him. I remember how Yoko was reviled by most of the people before, now their relationship has become a legend.
Also, much more is known about the Beatles music now, more than could ever be expected as far as writing and recording goes. Before as I'm sure you're aware of, Lennon/McCartney was thought of as a writing team when this in fact was a rarity. It's now known who did what in almost every facet of their recordings, so things like Lennon's humor and sarcasm are more easily recognizable.