Here is my humble opinion. I've stayed in all three a few times each and I live about 35 minutes away. Husband and I visit DL often because of the discounts we get and because we have friends in from out of town often. I've only been to WDW once before.
GCH is the most expensive. DLH is second, PPH is third. GCH is closest to the parks, DLH second, PPH third. That said, the layout of DLR is so much smaller than WDW, all three are walking distance from either DCA and DL. PPH and GCH is closest to DCA. GCH has an entrance to DCA. PPH can sometimes use the secret passageway to DCA (this closes and opens seasonally, though.)
Pools: The best pool is the DLH. PPH has a giant waterslide and little theming, but they do have a nice pool bar. DLH is well-themed and is a lovely diversion. GCH's pool to me was just a standard 4-star hotel pool.
Rooms: Based on this alone, I'd pick the DLH. The grand's rooms are very nice and very posh but very small. PPH are less expensive, okay-sized, and nicely basically Disney themed. DLH are the best themed, and you might even get a view of DTD from your room.
Check-in: The worst check-in I had was at the Grand. Hours and hours of waiting for a room is not my idea of fun, even though you can easily walk to both parks. PPH and DLH both were able to check me in every time at check-in time.
Lobby: The GCH wins, hands down. Again, I've only seen the WL at WDW once before, but this is most like the WL at WDW, I think, as far as decor goes. They have a great lobby bar, The Hearthstone Lounge, that has great hot chocolate in the winter (they have a grown-up and a child version, too!)
Service: Hhhm. Hard to choose. I've never had concierge at any of the DLR hotels, but it seems that PPH was nicest to me, then DLH, then the Grand. It just seems that the GCH has staff doing so much to make everyone happy, that personal touches have escaped me. The PPH was awesome to me the three nights before my wedding: I was met the desk with a bouquet of balloons and autographed Fab 5 photo congratulating me. Sam at the Lobby bar is my kind of barkeep, too.
Kids: Kids (we don't have any but friends' do) Most kids always prefer the DLH because of the pool and the Pixie Dust and the theming. My niece is most uncomfortable at the GCH, and another's kids loved the water slide at the PPH.
So, which is my favorite? The Grand. If I were on a budget, I'd take the PPH in a heartbeat. If I needed a weekend of Disney Magic, I'd take the DLH.
Also, expedia.com and travelocity.com often have great deals on all three hotels, so check that before you buy a package. It seems to me that I can always beat ticket/hotel packages by buying the elements myself, but if you have to include a plane ticket, a lot of the airlines' packaged deals are a better buy.
Please, do let me know if you have any more questions. I've also stayed at a few off-site hotels (some are even closer to the gates than the PPH and the DLH.)
