We have stayed at DL and GC. I love GC, and would prefer staying there myself. However, the DL Hotel is great, and our DDs preferred it. The Neverland Pool has the pirate ship and whatnot...more themed than the Grand Californian Pool.
Sooo...it depends on if you would like to please the adult preferences (but, hey, they still LOVE the GC-it isn't as if it is a "bad" choice for kids!), or really want to go full bore for the kid-pleasing aspects. Also, the DL is MUCH LESS EXPENSIVE. The GC is a closer walk to everything, but you can take the monorail from DL...
I myself am still deciding what to do this summer, and I am leaning toward GC because it is so easy to walk to everything. But I am not yet decided either!