I had a '96 Dodge with a 12v Cummins for 9 years prior to getting the '06 F350. I spent far, far more getting it to run really strong and it ate transmissions for breakfast trying to pull the same loads. It killed a Goerend transmission, Sun Coast tranny and 2 ATS trannies before I got rid of it. You want to talk about expensive! Still, with all the modifications, the best the truck would run in the 1/4 was just over 15 seconds and it weighed just over 7200 pounds.
With about a tenth of the modifications to the engine and with a completely stock transmission, I've towed the same with the '06 F350 all across the country. It also ran the 1/4 in 14.2 seconds when it weighed in at 8100 pounds! I really liked the Cummins and the really low RPM torque it had, but the 6.0 PSD in a much heavier truck is considerably faster and has cost me far, far less to keep going. I completely expect the 12v Cummins I had to still be running fine at 400, 500k miles. It will take several more transmissions to get it that far, but the engine will go that far. I know for a fact the Ford 6.0 PSD won't cost me any more money for at least another 120k miles. It's still under warranty until 200k miles. And, to be perfectly honest, I'm not the type to ever drive a pickup or car over 200,000 miles. So, in my case, the 6.0 PSD is more powerful, gets better fuel economy (remember, the 5.9 Cummins had some serious mods) and will last me as long as I need it.