Well, this advice may be wrong because we have never stayed on-site at Universal, but we are going with HRH over RPR because there are 5 of us and 3 are teenage boys. From what I understand the rooms are (much?) bigger at HRH and you have the option of paying more for a deluxe room with a pullout sofa, which is what we are going to do.
I think others will know more, but does RPR even have standard rooms for 5?
In any case, have a great time! I can't wait til our August trip.