Where to start? Gas Mileage please.

My wife is determined to purchase a 2007-2008 Ram 1500 Quad cab. I personally prefer my chevy but she wants to know which engine gets the better MPG. Even the salesman can't give honest answers.
So. How about some honest opinions.
5.7 ?
4.7 ?
Sorry, I was told however to stay away from the 3.7.

[fredjacksonsan]

The 3.7's not a bad motor, it just doesn't have a lot of power, and you'll be 2wd.

Between the 5.7 and the 4.7, their mpg's are rated the same(www.fueleconomy.gov). I've heard that the HEMI can get 20mpg highway if you're light on the throttle. Unless you want the manual transmission, I'd go with the 5.7.