I own an 05 Cummins and love it. Having said that I wouldn't buy a Cummins newer than 06, the newer trucks don't get the fuel mileage of the older trucks and have way more maintenance issues.
If I was buying a new pickup for occasional towing it would be a Hemi.
If I was going to do a lot of towing of an enclosed trailer I would buy the best 06 and older Cummins I could find.

Sheldon