I stay with Marriott because the full service Marriott brand offers a consistently good product. Even a "bad" Marriott is at least good. The full service Hiltons can vary from wonderful to awful. The same goes for the Starwood brands.

Where the Marriott family suffers is in the second-tier brands. Every Hilton Garden I've stayed in is a couple of steps above a Courtyard. Marriott does not offer a product like Embassy Suites.