Interesting discussion. I am a Marriott Rewards member going back to ca. 1985 or 1986 and used to prefer CY when I was not staying at a FS property.
Now I find FFI to be a better value. Most of the newer ones sport the Fairfield Inn & Suites moniker and I find the rooms to be as nice or nicer than CY. Now that I am retired the free breakfast is nice also. So when the FFI is $10 to $20 less per night for an equivalent room and free breakfast that is a no brainer. Oh and a lot of the FFI now have at least cardio equipment. But if not I can run outdoors.

Only downside is most FFI do not have pay per view movies in my experience. Not a deal breaker for me but I mention because have not seen that discussed upthread.