I personally like POFQ better than Riverside, it's a smaller resort, so there's just less people at it, less bus crowding, AND only one stop vs going through the entire resort for multiple stops. You can also use all the amenities of Riverside via staying at it.
-boats to FQ/Riverside available, and DTD
-pools, hot tubs
-running/walking/jogging path
-carriage rides
-Riverside has an awesome lounge with Yeehaw Bob playing, which can be an awesome time!
Now Coronado (IN MY OPINION)
would be my choice for a solo adult trip if i was planning on more resort time and thanks to it having the convention center and such,(simply because of the gym) there's usually more adults staying at the resort, and many more solo travellers.
-Lounges are great
-quick service is awesome, great food, build your own salads are delicious
-running/jogging trail (around the resort)
-they're the only moderate that has a GYM, so that's a major pull for me
-hot tubs & pools as per usual
Now, all in all, i do like POFQ MUCH better, but the gym is, as said, a major pull