Nicest of the IHG properties in DC would be the Willard, hands down. Next would be CP Hamilton.

CP Hamilton is a historic building with rooms of varying size, none particularly huge but all nicely furnished. There is a refurbishment in progress at the moment and the club lounge on the 12th floor is closed. They substitute complimentary breakfast in the restaurant which is quite good - better, actually, than the continental option served in the club lounge. New room furnishings are attractive but if coffee is important be advised that they have replaced the coffee brewers with the single serve type and provide only one or two capsules, and that godawful powdered whitener instead of real cream. There is a Starbucks in the lobby , though it has limited hours and no WiFi. Staff is generally quite pleasant and location is excellent. Some rooms can get street noise so if that bothers you ask fro one off the front.

HI Central/White House on Rhode Island Av is not as nicely furnished as the CP but it is OK for a HI and does offer a rooftop pool. I got breakfast chits on my last stay and the daily buffet with omelet station was fine. WiFi is free but notoriously slow and unreliable at this property. Same caveat about street noise in rooms along the front.

HI Capitol on C Street SW not as conveniently located but perhaps a tad more nicely furnished. Short walk to L'Enfant Plaza metro. Outdoor pool open seasonally. WiFi was fee, I beleive.

HI Rosslyn is a short walk from Metro station. Rooms pretty standard HI style but OK. I often get upgraded to a suite at this property and also get free breakfast in the top floor restaurant which has excellent scenic views, breakfast buffet nothing special but not horrid. There is an indoor pool but I have not used it.

HI Georgetown hard to get to and from without a car (which is a pain in DC) though they do have a shuttle that runs to the closes metro (Foggy Bottom.) Pretty standard HI all around. Not first choice unless have business in that area.