Right now, for me, it's simple: Marriott offers the maximum rewards earning bang for my buck. It also has multiple properties in the cities I travel to for business, so I always have backup if one or two of them are sold out. For example, next week in Seattle, both the Renaissance and Marriott are sold out - but both a Courtyard and an RI downtown have rooms. (And both of them are good properties. I'll be at the CY.)

Hilton is a close #2. As a Gold earning points+points, I find that their rewards earning power per dollar is almost the same as Marriott. But they don't have enough props where I need them. Right now, anyway. If my mix of cities changes, then Hilton might start to look better.

I wish I could say "Because Marriott treats me wonderfully and because their properties are unique, different, and exciting." But the reality is that all of these midscale hotel brands have become a commodity. A Marriott is a Marriott. To their credit, they do the midscale business hotel very consistently with adequate service and few major problems. They also appear to do the upscale properties well, but I don't stay in enough Ritzes and JW's - or St. Regises or Conrads - to really compare/contrast them all.