Ive had dinner a few times at the Park Hyatt but havent stayed there. I have stayed on the club level at the Grand Hyatt and it is very, very nice. Service was spectacular. I think the restaurants in the Grand are not as nice as at the Park. The Grand is newer, very new in fact, so it may not be as well known but it is a fantastic place. If you dont care about whether it is a Hyatt or not, I would recommend Seiyo Ginza. Also pretty new. A Japanese business owner in NY who travels frequently to Tokyo has for years recommended the Park Hyatt to us. This past year he said he has switched to the Sieyo Ginza. We stayed there a few days in March and it was a cut above the Grand Hyatt in service and room quality, especially size. But if you are looking for Hyatt points I wouldnt hesitate to stay at the Grand Hyatt.