We prefer FQ. It is, in my opinion, must more romantic than Riverside. They pipe in Jazz type of music throughout the day. There are lots of courtyards with benches in them and shade. There are benches, ducks, etc. along the river where you can sit and relax. The property itself is much smaller than Riverside. Therefore there are less people in the food court area, etc. And, it seemed like there were less people "bustling" around the resort. It just never seemed quite as "busy" as Riverside.
If you are in bldg. 4 or 5 .. niether are far from main building, food court, bus stop, etc. Depending where you are within the building will make a difference whether you are closer to the pool or bus stop. Would take about 4 minutes at most to get to anything.
The only drawback is that they don't have any quiet pools at FQ. You would have to walk over to Riverside if you didn't like the main pool at FQ. However, we always found a place a little bit away from the pool to lounge. Was nice. And there is an area with tables and chairs right by the pool bar that is also nice.
We like Riverside but between the two for romance ... especially an anniversary I would vote for FQ.