As long as you don't exceed the weight, towing, or axle capacity of the TV, you should be fine with what-ever you select. My biggest mistake was purchasing a TV that met all of my needs at the time, but then wanting a larger (heavier) FW later on. I couldn't do it because of the capacity of the TV.
I traded in my 2004 2500 about five months ago. I used it as a daily driver, and you're right, it didn't do very well on mileage. I got about 13.8 around town. But it was sure nice to have when I'd hook up the FW and head out for one of our infrequent camping trips.