Hyatt's promos are much better than Marriott's, esp. the FFNs. Marriott doesn't have anything like that. And IIRC, Marriott's travel packages used to be a significantally better deal, but the points needed were raised substantially.
In addition, for those who don't travel as much, Hyatt's elite levels are easier to get.

As someone who pays for travel all out-of-pocket, Hyatts and IC (I'm okay "slumming" it. ) help me get the most for my money.