dweber, I have a 05 F250 KR.  175k miles so far. You said its a dually.  Do you mean its a F350? 250 is single axle only. 350 can be had either way.

I am happy with my truck, however the 6.0 is expensive to maintain.  I've replaced the EGR and the Fuel Injection Control Module. These are the most common items to replace. But once done its a good motor.

I had a 2006 F350 King Ranch.I put 108,000 miles on mine before I bought my 2011 6.7L. I worked it hard towing almost dailly.the dealer

The FCIM seems to fail before 100,000 mile and so does the HPOP. I think I paid the dealer less than $2000 to replace them and several glow plugs.  That is a enough money to hurt somebodys budget. But once done, The trucks seem to run very well. 

This is what's spinning bearings and breaking cranks in the Duramax engines... Never heard of a stock Duramax with a bad crank...

http://www.youtube.com/watch?v=6Rpwn7i6L4Q

All I know is my husband brings home a good paycheck every week courtesy of blown up Duramax engines. Don't need anybody's mechanic to tell me that.

A direct comparison of the physical rod sizes should only be between the Ford and Duramax. Both are V 8's and share similar displacements. The CC displacement of the cylinders of both engines are similarly sized, yet the Ford rods have larger bosses and bearing surface areas.

The Cummins also has a similar total displacement as the other two engines, yet it has two fewer cylinders. Thus each cylinder has to be proportionately larger than those of the V 8s. Each piston and cylinder is larger to produce the same amount of overall volume. The rod sizes and bearing areas, are also increased to provide the necesary durability in their connection to the crank.

The comparison of the Cummins' rod sizes to the other engines is not an apple to apple correlation. Cummins, because of its well known durability, has obviously chosen well in its design specifications.

I have friends and neighbors that drive their choice of one of the big three diesels ( and some other neighbors driving Toyota and Nissan trucks)  Over the years I've watched ( or helped tow them) in for service. No brand is immune. 

It is so easy to chip or program modern trucks and any truck that has been souped up runs the risk of a shorter life or higher maintainence. The old saying, " If you play be prepared to pay" is very true.

I had a 2003 6.0L built the first week of production.  I left it stock and had a few of the problems that engine become know for.  VGT, ICP, FCIM and glow plugs.  I was never left stranded, All work was done under warranty. It had more power and better fuel mileage than my 2000 7.3L So other than 7-10 days in the shop over a 100,000 miles  I really couldn't complain about that truck.

My 2006 6.0L was asked to work harder. I had an Edge Evolution programer, That I always left in stock or ecconomy setting. I never once turned it up to powerful or race tunes. I used it more to monitor the engine, egt temps, clear check engine lights, reset the tire size etc. I also installed a B&D Performance Exhaust brake since I was towing a large 4h LQ and right at the limits for this trucks tow ratings.  I frequently tow up and descend 7-8% highway grades here in Utah/Wyoming. So I wanted the extra braking.   Again this 6.0L had pretty much the same common failures.  FCIM( fuel control Injector Module) HPOP ( High Pressure Oil Pump) and 4 glow plugs over the 108,000 miles that I owned that truck. Everything was covered under my 100,000 mile powertrain warranty, But If I would have had to pay, It was around $2000 in repair cost.

Maybe I had good luck with my 6.0L engines. Maybe the 100,000 miles I ran them before selling them off is just shy of where serious problems start to emerge, Maybe because I kept the oil changed every 5,000 and didn't program them to higher horsepower tunes, Maybe because I didn't abuse the engine I had no problems.  Who knows, My experience with the 6.0L was not problematic and I personally wouldn't avoid the engine, as long as it had been taken care of.  But I would put a nest egg away to cover the common problems if the truck is past 100,000 miles or its 5 year warranty.