MRDW point values are directly reflected on the dollars spent at the various Marriott brands, and are reflected in the Award point value when redeeming for the respective brand. The following link is lists the value earned at each brand:

Marriott Reward Points - Earned Value

The point redemption is basically (though there are several items that influence this (location, season, etc.) the same way. If they are running a special of some sort, probably best to pay. Being a GM, I would always recommend to use the points when I am running a weekend or get-away promo.

I hope this helps out.