We have stayed at HRH twice, PBH once (with another booked for this July) and have visited RPR several times. All three are beautiful hotels. We almost booked RPR for our upcoming trip, but the whole smaller rooms thing bothers me a bit. The great thing is, you can visit all three, use all the restaurants and, if you're a guest of one, you can use the pools of all three.
HRH is the best in terms of proximity to the parks. It's the only one where walking is a no-brainer. Walking from the other two is certainly possible, but you won't always feel like it. That means you'll need to take a water taxi (pleasant, but the waiting becomes a bit tedious after a while) or a bus. During thunder storms, the water taxis don't run.
Our teenage girls love HRH - it's really cool and they love being close to the parks and CityWalk. Having said that, staying onsite at any of the hotels allows them the freedom of coming and going as they please. We let them charge to the room and we hardly see them!