I've stayed at that Ritz about 10 times, maybe more. We have become friends over the past 17 years with one concierge working there - still stay in touch with her. We like the staff a ton, and that it's connected to the Galleria is nice in cold weather especially (when my kids were really little, they used to have a tiny food court on the 3rd level with Burger King, which came in handy, but it's not been there for years). The mall is very upscale and nice to walk (but other than Bloomie's I can't afford much there).
They also have a towncar to drive you over to Tyson's Corner Center (or any restaurant within a couple miles if needed). That's the largest mall in the Mid Atlantic.
The rooms are smallish, but nice. The club level is nice. It's a small quiet Ritz for the most part, and I do love it! If you can get a "junior suite" (they used to not have a category for this) it's got a king bed plus a small sofa sitting area, so it's got a bit more room. Last time we stayed there, we got that plus the connecting double room for our kids.
Much as I like this hotel, if you've got an early morning flight out of IAD, I'd go to a hotel right at the airport, maybe one with park & fly and can shuttle you there. It just makes things easier. Otherwise, I'd say the Ritz is better and you can walk right into the Galleria (and they have a few places for a nice dinner right there). You'll get your night credit (the other posting is incorrect) as well as some points.
We did this a few years ago at National - stayed at the Ritz Pentagon City for a night prior to an early flight. Didn't bother paying for club level, since we had to take a cab at 5am to get to our flight. Had a bagel at the airport!