My opinion--yours will vary->
All engines have improved in long term durability. My son has a 6.2 running strong at 196K with no oil use. It's time to forget the 6.0 diesel (unless you were personally burned). It was an International design. Ford bent over backwards to make sure the 6.7 was reliable. Yes, there were a few problems the first 2 years, but the transmission torque converter was actually a bigger problem. We had zero problems with our 2012 6.7 until about 80K. The 6.2 gets a 6 speed only in the 250, and it's actually a beefed up 150 transmission (TorqueShift-g). We get 19 - 20 mpg cruising at highway speed obeying the speed limit--15 around town--11 towing a 12.7K fifth wheel. Distinctly better than a gas engine. The higher cost of fuel does result in a similar cost per mile of fuel, leaving the initial cost as the biggest factor. However, I expect to replace this 6.7 with another because I LOVE all the HP that a diesel gets between 1000 and 2000 rpm.