If access to more restaurants and adult entertainment are your preference, then RIV - though be forewarned that the Skyliner closes one hour after Epcot closes, which likely means in September around 10pm. If you’re still over at Boardwalk at that time, you’ll need to take a Lyft/Uber, or bus to DS and back to RIV.
Personally, I’d choose CCV, but I absolutely love the Wilderness Lodge. Grand Floridian, Contemporary, and Polynesian are easy enough to get to if I desire more restaurant choices, but I love Geyser’s Point for a quiet dinner together, the Territory Lounge is a great little bar, and the atmosphere and solitude of the Wilderness Lodge is perfect for a couples getaway.
But admittedly I like Wilderness Lodge theming over Riviera, so it really depends on what your cup of tea is.