I think you get the picture OP. When they're good, they're really good. When they're bad, they're REALLY bad. I've driven Ford trucks most of my adult life because they've always been good to me. I bought my first travel trailer in 1999, and pulled it with a 1990 F250 that had the 460 gas motor. I wanted to get a diesel many, many times, but not willing to change brands (Yet, as I never say never), and hearing of the 6.0's problems, I waited. I almost bought a 6.4. Almost. Then I almost bought a 6.7 diesel when I bought new in '13. Almost, but bought the 6.2 gasser instead. It was (is), a great motor but we want to get a fifth wheel soon, so I traded it in for a new '15 6.7 diesel. Love it!
So there you have it. My .02 cents worth is to only echo what's been said. If you were buying new, I'd wholeheartedly recommend Ford diesel. used, as has been said, there are better options. Best of luck. I hope you find a great truck, no matter what brand.