Having stayed at both HRH and RPH (trying PBH for the first time this summer), if the kids are into slides, HRH is the place to be. Although the RP has nice theming (and the younger one may prefer it), there is no pool slide. There is an interactive water play area with cannons, etc. If you liked the pool slide at CSR, HRH is even better! The pool is zero-entry, which means the 2 year old would be save and comfortable, while the older ones were sliding.
Hope this helps!
P.S. I know PBH also has a slide, and I'd love to hear from "experts" as to how it compares to HRH.