Wirelessly posted (BlackBerry8703e/4.1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/104)

Do you have to stay at Marriotts? If you can stay at Hilton family properties (including Hilton, DoubleTree, Embassy Suites, and Hilton Garden Inn), you can double dip, that is, earn both Hilton HHonors points and airline miles for the same stay. And if you can stay at different Hilton family properties for some or all of the four nights on each trip, you will earn even more airline miles and reach Hilton HHonors elite status that much more quickly (based on number of "stays," rather than total number of nights).

Also, I think that Enterprise now participates in both the Amtrak Guest Rewards and Choice Hotels "Choice Privileges" program. If you are paying a qualifying rate with Enterprise, there's no reason to leave those points on the table.