my dad was a die hard chevy guy and was about to buy a toyota tundra, I told him to look into getting a cummins, he ended up getting a 06 megacab 2wd auto cummins and he get 25mpg. I asked him last week if he is happy with it and he said he wished he would of done it a long time ago.
As for the ford, a buddy of my dads who is a rancher had fords all his life, he bought a 03 cummins about 4 years ago. he said he will never pull with a ford powerstroke again, he said its night and day between the two.