I've stayed at all three in the past few years - HRH in November, RPR and PBH in July.
Getting from RPR and PBH to WWoHP-Hoggsmeade just about killed me. It was so hot... and so far to go... even taking the boat, it still felt far. This was early evening for events at WWoHP, not mid-day.
Getting from HRH to IOA or UO was a pleasure. Now admittedly, it was November so it was much cooler and less humid.
If your main reason for being there is to go to the theme parks, then I would definitely choose HRH.
If you plan to spend a lot of time at the resort, I know PBH has a great reputation, but I wasn't all that impressed. The beautiful part is that courtyard/shop/restaurant area near the water. If you're inside the hotel, you might see that part for 10 seconds a day when you glance out a window while walking by. I personally didn't think PBH was any nicer than RPR.
So my first choice would be HRH. My second choice would be whichever is cheaper (PBH or RPR). I haven't stayed at the new Cabana Bay yet, so I don't know how that would factor into my decision.