If you have to do a lot of towing a 7.3 powerstroke is indeed your best choice.. however, if you don't tow or haul extremely large loads, the diesel is a VERY poor choice. Maintanence on those big trucks is VERY costly. An oil change is 15 quarts, plus filter, plus fuel filters that have to be changed regularly. Brake parts are twice what a 1/2 ton costs, and large trucks wear tires way faster as well. WAY faster. The stories about diesels getting better mpg are mostly BS, and diesel, at least in my area is more expensive than gasoline. My brother has a powerstroke, and let me tell you, it's thirsty.
That said, the 5.4L 2v and 3v F150 trucks are proven to be good for 300k miles. The fuel milage isn't great compared to the other brand trucks of similar payload, but the engines really do run forever. It's what I settled on after wanting a diesel for a long while, it's just that after putting pencil to paper the extra money for the diesel wasn't worth it... and after watching several family members and friends (with service trucks)put 300k on 5.4's and still pass emissions testing.. That's impressive as heck. An LS engine won't do that, the dang lifters give out at 150k.