Rudi, as you suggest, Rewards are better for longer stays. My analysis indicates that for stays of 3 days or longer you are better off with Rewards. This is calculated strictly from a $ perspective with no preference to how you intend to use the award (free flights vs. free hotel stays). As far as switching, I've had problems with Marriott in the past. It seems that the computer system does not keep up to date with your preference! I would make it absolutely clear to whoever you talk to at Guest Services AND the front desk when you check in, which one (miles/rewards) that you want!