JW Marriott is best location, and a very nice property. My only complaint there is the gym - it's horrible and I ended up buying a short-term membership at a real gym to manage during the week I was there recently.

None of the DC lounges (FS properties) are open on the weekends and neither JW nor Renaissance offer breakfast certs for plat members - believe me, I called them all when planning my two recent trips. I did get a nice young man at check-in at the JW who responded to my incredulous "Plats really don't get breakfast on the weekend here?" with a two day buffet pass, which was nice, though certainly not necessary.

Mayflower is nice, but I don't know what category they're in. Wardman Park is in a very nice setting and recently renovated, but I've only spent one quick night there and wouldn't presume to recommend or not recommend based on that.