Yup, the newest 6.0 PSD has been a nightmare and the newest twin turbos look to be the worst. A buddy of mine bought a new F350 6 months ago and it looks like a sonofagun to work on. The service book says you have to pull the radiator in order to change the fan belt.
Yep... if there is cylinder head service to be done on the new Fords... you have to pull the cab off the frame to get to them... fun stuff...
The 6.0L PSD I had was an '06. I didn't have any problems with it, but I had heard all the story's about it. Of course after I bought it. A lot of guys I know had nicknamed them "6 Leaker" since the main problem was oil leakage from the 2 piece block. Also there were some major issues with the seals between the turbo and the block. I got lucky I guess... but the truck is long gone.
Ford is still in litigation with International over who is to pay for all the warranty work that was done on all the recalled 6.0L and 6.4L PSD's... as far as I know International is no longer going to be supplying Ford with diesel engines. Ford is going to do it all "in house".
The Duramax (made by Isuzu) is a great engine as is the Allison auto trans. However, just like in the past... GM is always the last one to the party. While Ford and Dodge were proudly pumpin' out great diesel trucks in the 90's, GM finally stepped up in 2001 with the Duramax. The 6.2L and 6.5L GM diesels were a joke. Quite possibl;y the most worthless diesle engines ever put in a truck. So the Duramax was a welcome addition to the GM lineup. Too bad GM didn't get their act together sooner.
Cummins has been a winner for years. Look in almost every Cat, Skidder, long haul truck, logging truck, and now lots and lots of motorhomes... you will prolly find a Cummins. The venreable Cummins 300 has made it's mark, and set the bar for inline 6 diesels. The 5.9 turbo diesel in the light trucks for Dodge are based off of the big ol' 300's design.
So for "NEW" trucks... I would prolly get a Chevy/GMC or a Dodge. Ford still is having problems with the 6.4L. For "OLD" (1995-2001) you can't beat a Ford 7.3L PSD. However the Cummins in the Dodges of the same years are fantastic as well. It's just the Dodge trucks are so damn ugly...
Stay away from any GM truck with a 6.2L or a 6.5L... they aren't even worthy of being called a boat anchor... scrap metal is more like it.
Gary