I'm a huge Pearl Jam fan, and I've got to go with them on this just for Jeff Ament.
Don't get me wrong, DeLeo is awesome, too. But Ament has a way of absolutely carrying the songs in a very subtle way. Ament is either rocking hard at the front of the song, like in Go or Jeremy, or he just hangs back and supports the song, like in Black or In Hiding. No matter what the song is, though, if you take him out of it completely the whole thing falls apart.
DeLeo does have some fantastic Jamerson-esque melodic lines. It just sounds like he's playing in the wrong band sometimes. Listen to something like Interstate Love Song, and it's like DeLeo's thinking "Oh, you guys are gonna play that riff over and over and over and then just end? Alright, I'll just do my own thing 'til the song's done."
Edit: I'll also say that I think a lot of hate for Pearl Jam comes more from a distaste for the fans than the music. I've been to several shows, and even though the band puts on a hell of a performance, they do attract a certain...unrefined crowd.