Never stayed at the IC Tokyo Bay or IC ANA Tokyo, but the Strings is a fantastic hotel in a great location next to Shinagawa. The IC ANA is in a somewhat more inconvenient location (vicinity of Roppongi; you'll need to use a taxi or Namboku subway line), though I have at least been to the bar on the top floor and found they poured a very good drink or three.

As for Narita, while the CP ANA is better than the HI, the HI's newer rooms aren't bad (you should get one automatically as a Plat) and the HI tends to be dirt cheap. The restaurants are pricey, but their grilled codfish teishoku set is way better than you would expect at such a touristy hotel.

Totally agree with bmttokyo that you should pay cash for the HI and save the points.