Grand Californian: I've always dreamed of staying at GCH someday, it's
so gorgeous, though it doesn't have as much Disney theming as the DLH. Shorter walk to the park entrance. However, it's the most expensive of the three by far; if the numbers were a bit closer for me (ie. with a screamin' deal!) I would splurge.
Disneyland Hotel: We have stayed here numerous times. The pool area is great, though I haven't seen it since it's been remodeled. We also enjoy the grounds here: waterfall area including koi pond, the restaurants (Goofy's Kitchen is a big hit with the kids), the gazebo and topiaries. The hotel is older, so the rooms tend to be a bit larger.
Paradise Pier: Least expensive, and compared to DLH, a shorter walk into DCA via the GCH! Not as much outside of the room of interest as the DLH, though of course there is a small pool area, and I believe it has a slide. My kids and I are staying here on our next trip, and they requested the PPH character breakfast over Goofy's Kitchen, to my surprise. We decided to save a little more money on hotel to have more for FUN in the park.
I think you'll be happy with whichever you choose.
