It really depends what you're looking for.
Here are my opinions:
Best Pool:
Advantage:
Disneyland Hotel
Quietest Atmosphere:
Advantage: Paradise Pier
Best Lobby:
Advantage Grand Californian
Best Quick Service Restaurant:
Advantage Grand Californian's Whitewater snacks
Best DCA Paradise Pier View:
Paradise Pier Hotel
Best DCA view of the Condor Flats area & GRR
Grand Californian
Best View of DL fireworks:
Sierra tower of Disneyland Hotel
Best romantic spot at a hotel:
Disneyland Hotel's Waterfalls.
Best room interiors for adults:
Grand Californian or Paradise Pier
Best room interiors for wee ones:
Disneyland Hotel's new "Pixie Dust" rooms
Closest Proximity to parks:
Grand Californian
Great old disney art to see:
Disneyland Hotel (and a few things here and there at Paradise Pier)
Basically: The Grand Californian is our "deluxe" except that the pool has very poor theming. Think of the resort as a cross between WDW's Grand Floridian and Wilderness Lodge. It really is gorgeous. The Paradise Pier hotel has a very relaxed "convention" type atmosphere, but they have added new disney touches. It is sort of like the Contemporary to me. They put in a disney bit here and there, but it is more of a typical hotel then the other two. The Disneyland Hotel definitely holds a ton of nostalgia to me (of course, most of my nostalgia left when the whole pool area was redone when Downtown Disney opened). My preference personally goes to the Disneyland Hotel. I love the theming of the Grand Californian, but it just isn't my thing...(I like my rustic to be rustic, not opulent - although I do love the car out front). Also, although there are some small rooms in all of the 3, the Grand Californian seems to have more than the others, and if you get a room above Downtown Disney, you may have some noise issues. I've never stayed at Paradise Pier, although it seems as though the rooms are larger than expected by most, when reading posts.
I hope this helps
Toodles
~Tina