A minor correction to emerold's post. Starwood platinum can also be reached by nights. 50 nights/year get you there.

While I like Marriott's consistancy. Their high end properties do not come close to Starwood in turns of quality and quantity. On award travels with Starwood, it is not uncommon to get a suite at places like Westin St. Frances or the Royal Hawaiian.
With Marriott, you can forget which city you are at. It's always the same.