If you have young kids (like 5 and under) who can't swim on their own without a life jacket, then they won't be able to use the main waterslide at the
Disneyland Hotel, and they don't allow the kids to wear life jackets on the slides at the Disneyland Resort Hotels. (The lifeguards make younger kids take a little swim test before letting them go down the slide.....nothing major......as long as they can dog paddle their way around then they'll be fine.) Otherwise, the Disneyland Hotel is a great place to stay! Their pool is great, they have a huge hot tub, pretty grounds, they have a really nice quiet pool, it's about a 3-4 minute walk to the DTD monorail station, and a nice stroll through DTD and the Grand Californian to get to California Adventure. Our room was plenty big, and had a sofa that could fold down into a twin bed, but a few rooms don't have a sofa and are smaller than the one we had. Make sure to request a room with a sofa......it's just a request, but one I would make.
If you do have younger kids who can't swim on their own, then the only water slides they can use is the one at the Paradise Pier Hotel (which has a great slide and the longest in the area), or the slides at the Howard Johnson's new "Castaway Cove" water play area.
Both are great hotels (we've stayed at both a few times) with large rooms, and walking distance to the gates of the parks are about the same (although the Paradise Pier is only about a 5 minute walk to the Downtown Disney Monorail Station, which takes you right into Tomorrowland in Disneyland).
Have fun wherever you stay!
(Here's a link to the Howard Johnson's photo gallery/web site if you're not familiar with the hotel.)
http://www.hojoanaheim.com/gallery/