There are at least 4 SPG properties that have free shuttles from Dulles: Sheraton Dulles, Sheraton Reston, Aloft Dulles, and Westin Dulles. And it seems to me that I've seen seen 2 Westin shuttles, but I'm not sure where the 2nd one is from.

I've had good experiences at all 4 hotels, although there is a horror story on this board about the Aloft. Certainly one can't argue with choosing Westin Dulles; as noted, they give free breakfasts to Plats. On the weekend that is usually true for Plats at Sheraton Dulles, as they typically upgrade Plats to Club Level, but since the lounge is closed on weekends, they give you a free breakfast instead.

The one thing that is not great about all of them except Sheraton Reston is that they're not within walking distance of much. But for a 1 night stay, that shouldn't be a problem. Enjoy your stay. tls