I've owned a few over the years, I have worked on several and have driven several more here's my rundown. My 01 F150 4.6 V8 was a good truck but 19 mpg is achievable with the new bigger V8' s that put out more power. I did find the 4.6 lacking for power on several occasions. My 04 and 06 Dodges with the pre emissions Cummins were great trucks. The biggest issue was the body and that became a huge issue. If you want something to keep you safe in a crash they fold up like tinfoil. My 05 1500 Dodge Hemi was awesome, tons of power 17 mpg and fun to drive had the same body as the 04 and 06 though. I owned an 08 Powerstroke for a little over a year before the dealer bought it back, that should be a clue. I now drive an 09 F150. The power, transmission, roomy crew cab and towing capability of this truck make it one of my favorites. The new Fords are tough to beat. As for some of the other models that I haven't owned but have experience with, the 6.0 Powerstroke was a terrible motor however there are several on the road with a ton of trouble free miles. Those are generally 06 and newer or older ones that had 06 or newer motors put in them. The 5.3 chevy is a good dependable motor and as long as you can find one in a vehicle that has working gauges and you don't need to pull much they are a good option. I have known several 6.0 GMC and Chevys the new ones seem to be a little better mileage wise but the older ones were gas hogs. Dodge has been putting out competitive trucks for the last 10 years and aside from the issue of their thin skin they offered one of the best engine / transmission set ups until the 6 speed Fords and are a good option as well.
Now that I've shared this with you I'll give you the insight of someone who has averaged 1 new vehicle purchase a year since 2004. Buy what you like. Don't let the hood ornament influence your choice as much as your seat of the pants opinion. I work with a guy who is so set on buying a Chevy every time that he has managed to lock himself into some crappy deals because he wouldn't think of owning anything else. Every company in the truck market makes great trucks. Every company has a lemon leave the line from time to time. Do your homework find what you like in your price range and you will be much happier making the payments.