Depends on budget, but the ANA IC in Akasaka (near Roppongi) is a very nice hotel and is close to lots of restaurants, shops and pubs (Ark Hills and Roppongi Hills). Its rooms a small compared to The Strings IC which is situated adjacent to the Shinagawa Train Station. The hotel is great with the rooms much bigger than the ANA. Access from the Airport is straight to the train station and walk about 200m to the hotel. Again there are lot's of shops and pubs nearby.

I prefer The Strings now as an RA due to the great upgrades they provide (never received an upgrade at ANA IC)