All three hotels are in the Shinjuku area. The Hilton and the Keio are near each other, and only a couple of blocks from the station. The Park Hyatt is a bit farther away, and the walk to the station is about 15 minutes. I've stayed at all three. By far, the best one of the three is the Park Hyatt, but you will pay for it. The Keio and Hilton are NOT in the same price and quality league. Having said that, they are both very good hotels, and you can't go wrong with either. The Keio is the most convenient to the west exit of Shinjuku. If your business is in Shibuya, it is a straight shot down the Yamanote line. You can be in Shibuya in 10 minutes station to station.

If it was up to me, I'd pony up the extra 10,000 Yen from my own pocket to stay at the Park Hyatt. My favorite hotel in the whole world. You will not be disappointed.