The way I've done my math is that for a routine hotel stay in a tier 3 US city or an airport hotel Starwood usually gives better earning rates for one night stays and Marriott for 3-4 night stays (due to the Starwood Plat welcome points, especially at the moment with the bonus). For stays in major hub cities or expensive holidays I see the points earning as enough of a wash that I don't reflect it as a factor.

In terms of redemption, I value my hotel points quite highly for use in hotels and have noticed that Marriott often seems to have the better value but as I usually use redemptions for leisure purposes I normally prefer to go with Starwood, particularly given the significantly better treatment I get there. The lack of proper program integration of the Bulgari, Edition and RC hotels is a major negative to the Marriott program for me.