I traded an '05 for an '07 because I wanted bucket seats and a 6 speed tranny (better mpg). I was running the Predator v2.02 @ 65 hp, stock tires, egr disabled, and a swiss cheese factory airbox. I got 18 mpg on country roads @ 60 mph and 20 mpg on the hiway @ 70-75 mph. I was a happy camper. I am currently running the EVO @ 60 hp, and have previuosly run the Predator @ 65 hp. I have 256/75/16's on the new truck. I get 16-17 on the same country roads and on the hiway so far. From a fuel economy standpoint and my wallet, I wish I would have kept the '05. Even from a power standpoint the '05 feels equal to the '07. From a warranty and comfort standpoint, I am glad I got the '07. If the fuel economy improves, I will be tickled to death and never look back again. I've only got about 8k on the truck so far, so I do think mpg will improve some. BTW, I got my two best mpg tankfulls on ULSD. (17.2 and 17.5) I got 17.1 once on LSD, everything else has been in the 15's and 16's.
Bottom line is you can't really go wrong with either truck, although your mpg seem awfully low. I'd take either and be happy. But that's just me.