My two cents:

Forget Crystal City. Though not far from Metro, it's the farthest walk to a Metro station of any of the three ES in town. And the walk ain't exactly scenic.

I generally despise sending tourists to stay in the suburbs, but I will reluctantly concur with the ES in Alexandria as being the best choice for tourists. Don't be under the impression that it's in the middle of Old Town Alexandria, however, because it's not. It's surrounded by office buildings and overlooks the Metro parking lot. It *is* across from the Metro, though.

The ES in Chevy Chase is atop the Metro and lots of shopping, but as others have said, you can shop anywhere. It actually does not take that much longer to get to downtown from Friendship Heights on the Red Line than it does from King Street on the Yellow Line, and because the FS station is technically in the city, the rush hour surcharge will be lower. By the way, the Embassy Suites in Chevy Chase is not in Georgetown, though I suppose theoretically it's not that far in terms of mileage. Forget about walking there, though.

All in all, I'd say it's a toss-up; I live close to the one in Chevy Chase, but work near the one in Alexandria. Go for the one with the cheaper rate.