Even though PO-R is huge (and I do mean huge) it's a delightful place to take a stroll, a tandem bike ride, horse carriage ride. I also like the theming of the main pool better, and the fact that there are so many "quiet pools" on-site. Riverside also has a full-service restaurant which makes butt-kicking omelettes in the morning. FQ only has a food court and pizza delivery. And their lounge has entertainment most nights, I don't think FQ's lounge does, though I could be mistaken.
Now, granted, you might be a hit-the-parks-from-dawn-to-dusk kinda person, eating most meals in the parks, only using your resort as a place to shower & sleep. But I figure, if you're asking which is better, it's because you intend to take advantage of some of the amenitiesthe resort has to offer. My preference, hands down, is Riverside, but if you really prefer smaller grounds (or are traveling with someone who can't do so much walking and you worry about not getting a room centrally located) FQ is very nice too, plus a short walk/drive to Riverside if you wanted to check it out.