Re Mandarin Oriental, I rather don't understand the comment about nowhere to get tea/food/snacks. There is the casual all day restaurant k'shiki, and there is an area adjacent to the lobby with tables for afternoon tea or to sit and have drinks in the evening with great views. And, don't forget the casual Italian outlet on the lower floors operated by MO, as well as other restaurants in the same building such as the very good Sakuragawa.
MO has possibly the strongest overall F&B of any hotel in Tokyo, rivaled only by Ritz-Carlton and The Palace. However the Palace is somewhat different as they have restaurants that are essentially tenants, and are operated by top local restaurant groups, so therefore it no wonder why they are so good...