Depends on if budget is a factor or not. I'd probably stay at GCH if money isn't an issue. It's a beautiful hotel, RIGHT there, can't get any closer. Some of the best views are at this hotel IMO.
Second DLH, we love the themed hotel. It's the most Disney themed out of the 3. From the room decor, to the Peter Pan themed pool. To the little jungle boats you can drive. The grounds are really nice, complete with waterfalls and koi pools. We saw Goofy more then once walking around the Lobby, and of course there is Goofy's Kitchen in the hotel for Character Meals. Also has great views, we've had a pool view twice. And I tell ya, I spent a lot of time espeically at night just looking over everything lit up. They also have the view of DTD, which you can see the fireworks from. I hope to get that view someday!
We haven't stayed at PP yet, I'd probably stay there if budget was a bigger issue. As it is the cheaper of the three. You can get from what I understand some great views of DCA. It does have some theming, but not as much as DLH. They also have a character breakfast (Lilo and Stitch) in the hotel. They have a pool that is up high on a roof top (but not the top of the hotel).
I'd be pleased to stay at any, but that is in the order that I would choose. We stayed at DLH last month, and just loved it. Next year we are hoping for GCH! Good luck!