Our last two trips to UNI have been at RPR (3 years ago) and HRH (last year). RPR was a mixed bag for us - we liked the relaxed setting and ambiance but thought the pool area was just nice. Our trip was also tainted by having extremely disrespectful neighboring guests that stayed out late for HHN and then came back and made copious amounts of noise. I had to complain to the front desk and also bang on the walls - finally I had to confront them directly at 2am. Needless to say, not the most relaxing trip (that wasn't the hotel's fault .. but they didn't offer to move us or do anything else to help the situation either, which was disappointing to say the least).
Anyway, HRH has a slightly more amped up feel (see what I did there?) as the name would suggest, although once you get out of the main lobby the vibe is more relaxed. We found the pool area to be much better than RPR, with more beach/sunbathing space and also various quiet, secluded areas. Our kids (10, 7) preferred HRH as well, particularly due to the the afternoon pool activities which were very well done. We did, however, also have a parking issue where I was incorrectly billed (and had to return the next day and jump through some hoops to get a refund) as well as multiple problems with our door key, which resulted in several trips to the front desk and hours of being locked out of our room while maintenance tried to fix it repeatedly. This was a big inconvenience but I have to say that the staff went the extra mile to make up for our lost time, by giving us multiple free drink vouchers, two days of free breakfasts at the Kitchen as as well a movie kit with a free in room movie, popcorn and a candy package. All in all I think we got $250-$300 of credits on our bill - thats how you get repeat visitors, which is why we're returning this September as well.
I suppose the bottom line is that RPR is generally more relaxed, has nice restaurants and a more quaint pool area. HRH has a higher energy feel, fantastic pool area and great restaurants .. and is also a shorter walk to the parks, if that matters.