Really depends on what you value (and whether you know which rooms to avoid at Bayview). The Marriott breakfast is abysmal and there's a fair bit of traffic noise from Jamboree. But the hard product is way better than the Hyatt, it's right on the Back Bay trail, the west-facing rooms are very pleasant, the location is central, and you can park for free right down the hill. I enjoy staying at the Bayview quite a bit, particularly as a runner who values the trail access highly. By contrast, the hard product at the Hyatt is so poor I would never even consider staying there again.