I strongly prefer the RP, the pacific tropical theme is one of my favorite themes, it is a great resort. To me Hard Rock is just kind of blah in the theme and decorating department, kind of sterile looking like a hospital. But that's just my opinion. I am thinking the RP pool is going to be a lot better suited to younger kids as well, it has a cool splash playground area at the RP pool and I do not think there is anything like that at the Hard Rock pool. I also prefer the restaurants at the RP over Hard Rock.
Now out of the sense of fairness I have never stayed at the Hard Rock, only walked around the resort, so I know nothing of the rooms other than what I've seen in pics people have posted here, and my opinion is derived from that. But I have checked out the pool and other parts of the hotel. Don't get me wrong, its not a bad place at all, it is nice, just not on the same level as the RP IMO.