Agree with earlier poster that Hyatt offers the best rewards program of the three you mentioned. Hyatt redemption values are also much better and generally they treat their elites well. For example, one can often find Hyatt stays for 5K-15K / night whereas Marriott is typically 25-40K+ for comparable properties.

Hyatt does have a much smaller footprint so depending on your travel patterns, you may find it easier to earn/maximize your stays with the Marriott brand.