It actually comes down to personnal taste. My wife and I have stayed at RPR twice and PBH once. This coming October will be our third time at RPR.
I like PBH better while my wife likes RPR better. I like the look of PBH better than the look of RPR. When returning from Citywalk to PBH via boat, I find the view spectacular, especially at night with the lights on and the plaza music playing in the background. At Christmas time, they have a decorated Christmas tree on the plaza.
Of course RPR has its positives too. It's closer to Citywalk than PBH and is usually cheaper. It also has one of the best restaurants I've visited in Emeril's Tchoup Chop. Plus, for some odd reason, I like RPR's breakfast buffet (at the Island Dining Room) better than PBH's breakfast buffet (at Trattoria del Porto). I think that it was a combination of the fact that our server at Tratoria del Porto was hardly ever seen and that the Island Dining Room is nicely designed. Also, the check-in area at RPR is nicer than the check-in area at PBH.
My suggestion is if you haven't stayed at either hotel yet and are looking to save some money, stay at RPR. You get the same important amenities (FOTL, boat transportation between Citywalk and the hotel, good service) at both hotels. Let us know which resort you stay at and how it went.