I'll put in a vote for Marriott..... like IHC/HolInn, Marriott has wide range of hotel brands/prices which also puts them in the most places. You have all the options of staying at low-cost places for points to add-up for a freebie at a high-cost place, or vice versa.

There's just not enough Hyatts, even with Hyatt Places, to be sure to get enough nights if, like me, someone decides which cities you go to fairly randomly. (Although Hyatt is my #2 after Marriott.)

Small-town Hiltons, SPG tend to be so inconsistent, in my experience, while Marriotts are more reliable.