My heart is at GCH but I still enjoy DLH.
GCH:
Why I love it: maybe because it was my first onsite hotel but this always feels like "home". The Disney bubble is practically impossible to pop when staying there, the theming is beautiful. The access to DCA is amazing. I love GRR and being able to change into a swimsuit in the room and ride it over and over (yay single rider) during summer and go right back to the hotel is awesome.
-recently refurbished, idk if I'll like it having not seen it so I can't say for sure if this is a pro or con but it is something to keep in mind (I'm 99% sure I'll still love it- rainfall. shower. As a tall person that's music to my ears!)
Cons: just because I love it doesn't mean I don't see some downside (besides that ouch price point!). Rooms are small, the pools are themed to boring, the waterslide is also themed to boring & if you have an unfortunately located room it can feel like you've walked halfway to the CA beach by the time you get to your room.
DLH:
Why it's 2nd: I haven't stayed PPH so DLH is #2 by default

I've stayed at DLH twice and would happily stay there again when I have the budget to stay on-site but would like to save some money.
Pros: monorail is SO CLOSE! If you're staying in Fantasy or Adventureland Towers it's amazing how fast you get from the monorail to your room (better be one thin hotel they're building in that space...). Theming is indeed magical, love the light-up headboards despite my age. The pool is fun! Slides look great but I never have the energy to climb that staircase to try them after a day in the parks! We got upgraded to a pool view at check-in last time & I actually really liked it. The tiki torches at Sam's and along the paths seemed to stay on all night and I loved going to sleep with that view.
Cons: longer walk to the parks if you're not taking the monorail. I always felt like I was leaving the "bubble" transiting between park & hotel, doesn't have the awe-inspiring feeling the Grand does every time I walk into the lobby. (GCH takes my breath away every time and that in itself adds a dose of happiness to my trips.) The theming is VERY Disney, I see enough Disney in the parks that seeing it all over the hotel could feel like a bit much at times. Also, it felt like it was already ready for a refurbishment, but maybe it was just the rooms I had.
Btw- if kids were in the equation I'd do DLH, the theming that I see as a "con" is most definitely a "pro" for young kids!
Honestly, you can't go wrong with either of these hotels (as I said can't comment on PPH since I haven't stayed there). You want a more upscale feeling hotel, with updated rooms & rainfall showers? GCH. You want quintessential Disney and to feel some of that classic Disney? DLH.