Owens had a top gear that was just insane. Dez is more agile in terms of getting his body in position to get the catch or to stay in bounds. As far as route running goes, early in his career it was a problem for Dez not knowing what to do, but the book on Owens even in Dallas was that he knew the routes, but that he'd consistently break them off and run to day light and hope/expect/have a fit if the QB didn't see it and accommodate him. Now, a lot of *that* was because he knew damn well he would make a big play if the QB saw it, and he could. But it lead to a lot of picks for him not being where he was supposed to be. So, if you know the route and the adjustments and just won't run them...well, that's the same thing as not knowing them at all.
I think, back allowing, we're going to see Dez have a stretch here where you see Dez's career get into that rarified territory TO lived in for so long. TO's high-mark for TDs is 15. Dez has 14 right now, and has crept up 12, 13, 14 the last three years. Same average Y/G for both players. Remarkably close for both at this point, actually.
TO was the epitome of what I like to see in a WR on game day. And was poisonous enough that he was not worth retaining on a roster, regardless. Dez is 1000x the teammate TO was, even on a winning team. I don't think there's really any question about that.