I like the Reston the most for the hotel - really classy - and its easily walkable proximity to the rest of the Town Center complex, shops and dining establishments. Oh, and it is not an old town center. Created in - what - the '90s out of forest. All very modern. When I stayed at the Reston, it had a shuttle to IAD.

I like the view from the HR Dulles, which sits up on a hill, and there isn't anything for many miles in most directions.

The Fair Lakes is in an office park. Nothing to distinguish it, IMO. Meh. But the most convenient into DC by car.

If you wait until a couple weeks ahead to commit, you're very likely to see rock-bottom rates at all of the DC area Hyatts. But you have to keep your ear to the rail for the lowest. The Fair Lakes can be best - but there can be surprisingly - relatively - $80 - good rates downtown - even at the Grand Hyatt. DC is a ghost town around Thanksgiving, and Christmas to New Year's.