They are what Disney calls "sister" resorts. Both resorts have the same size rooms...about 314 square feet each. Both have the same type of furnishings....two double beds, a table, two chairs, an armoire, a bench and small table between the beds. Both resorts have bathrooms that are similar. They are two sinks that are separate from the tub and shower. There isn't a closet, per say, but a rack alongside the wall by the sinks. You can also get a room with a king instead of two doubles.
The difference between the two resorts in regards to rooms is in the theme. Riverside has two sections: AB which is more of a down south theme...very rustic in the decor. Thse are two stories and do not have elevators. Mansions are more of an elegant down south theme...like mansions. Grounds are much more manicured and inside the rooms is not rustic but more "elegant" for the lack of a better room. These are three stories and do have an elevator.
At Riverside, itself, there are differences. First, it has over 2000 rooms compared to about 1000 at FQ. It is a larger resort with 6 pools including a large theme pool. It also has a fishing hole. You can rent bikes, scurries, watercraft from the marina at Riverside. If you are staying at FQ you have to go to Riverside to do this. They no longer offer those services there. It is about 10 minute walk...and they have shuttles and boats that go back and forth. Riverside also has a sit down restaurant - Boatwrights that is open. There is not one at FQ. Both have food courts that are similar. FQ was just renovated but the posts on the board lean towards it being similar to Riverside and nice. There are stations set up where you get your food and then pay for everything on the way out. There is a good variety at both food courts. Riverside has a great piano player/act at the lounge in the evenings. I'm not sure what FQ has now...they used to have some very nice jazz players/bands. Both have lounges that kids can be in. Both have pool bars. Both have playgrounds. Riverside, does, though, have a fishing hole. But if you are staying at FQ you can also use it (for a fee...no matter which resort you are at).
The two resorts share transporation. FQ is the first stop on ...then it goes to Riverside. FQ is also the first stop off...in the evenings that makes it nice. Both resorts have the added bonus of there being a boat that goes to DTD. That is a nice perk.
FQ is more of a clean or "sanitized" New Orleans. Interior of rooms is decorated in New Orleans style. Nothing fancy but adequate for us. The decor of the mansions is probably the nicest, in my opinion, but we do prefer FQ.
We like FQ because it is smaller. Doesn't seem quite as busy. Every thing is very compact. I don't think there is a bad room in the place. Everything within a 5 minute walk. The gift shop at FQ is smaller than Riverside (Riverside has a really nice one.). But the one at FQ has everything one would need. Both have arcades. Riverside used to be larger than FQ but I heard the one at FQ was just rennovated so.... All bldgs. have elevators in the middle of them so you aren't really very far away, no matter where in the bldg. that you are.
The theme around the pool/grotto area is very nice. Very whimsical. Alligators palying instruments and a court jester. My son really likes the serpent slide. And there is a kiddie pool. There are, though, no quiet pools -- just the one big pool and a hot tub.
Let me know if you have any specific questions. We have stayed at both and are returning to FQ in Nov/Dec.