Having stayed in both, I would definitely recommend the Hyatt over the Marriott. Although both hotels sit side by side, and you can easily walk from one to the other, all of the Hyatt rooms (at least in the "old" tower) have water views, and the public areas are much nicer and more tranquil. In contrast, on my previous stays, the Marriott public areas were always jammed up, noisy, and full of conventioneers, the rooms are not as nice, and many of the rooms have non-water views.