Honestly the Grand Legacy is sounding pretty great! I wish I had tried it to compare (or that @93111tink had tried Fairfield). A long, long time ago I stayed at a couple different places on Harbor that I didn’t like but I’m sure they’ve all been refurbished since then.
The Fairfield is about as nice as a normal Fairfield that I’ve stayed in in many cities (I am a Bonvoy member so Marriott is always my preference). The rooms are clean and recently refurbished. Beds are comfortable. They have several room configurations that you can see when you book. I was looking the other day and I think one configuration was two queens plus a sleeper chair. They also have a king plus sleeper couch, which is the room I stayed in. The “Themed Rooms” were nice but probably not worth a lot extra - I think it was like a $10 difference my nights so I sprung for it. The walk is not far at all.
Good luck!