I got to say all these failures I've read is statistically insignificant and not weighted since Ford has now produced 500,000 6.7 Power Strokes from 2010 to 2013 vs. 2,000,000 Cummins from 1989 to 2012 vs. 1,500,000 Duramax from 2000 to 2013. :R
Repairs at the Ford/Chrysler shop my cousin works at since '93 have dropped so significant that he has been transferred to the other side of the parking lot to work on cummins/RAMs exclusively. As of 12/13 the Ford shop has replaced (1) 6.7 psd which is way less than the 6.4 psd and the common rail Cummins engines have been replaced in the last 3 years.
Here's a simplified summary as others like to express:
Ford = McDonalds
GM = Burger King
RAM = Wendy's
At the end of the day they all produce a turd! :B