Hyatt has in Europe less distribution - and in USA I normally achieve better prices at Marriott/Hilton.

At Marriott, prices (AARP rebate at least 50% for people over 50) are very competitive and even on those dicounted rates (example: Marriott-San Francisco Airport, this weekend, $ 85 AARP-rate-21-days-advance-paiement) full mileage credit (500 miles for one night and 2'500 bonus per 5 nights). And (till now) never a mileage-credit problem (one email solves it in 48 hours). Marriott (sometimes but less Hilton) is my choice for one-night-stays (50% of them at airport-locations: SFO, SEA, ORD).

I prefer Hyatt as Resorts and for longer-stays (my favorite: Hyatt at Beaver Creek, CO for skiing) and, as an exeption for one-night-stays at MCO.