I log 140 nights a year on average and have stayed with Marriott for the past 4.5 years. I am now slowly switching to SPG. I am only staying at Marriott for promotion (to ensure I get lifetime Plat) and for locations where Marriott is more convenient. But if rate is > $180, I usually select Marriott. With the green choice, I feel SPG more appealing if the rate is low. For expensive rate, the delta of points earned is low for SPG, but big for Marriott. So rate > $180, i stay at Marriott, else at SPG (for equal convenient and quality)