FWIW.
Had 2 F350's (MY 2004 & 2006) that had plenty of power for my 18k 5ver and were not at all unpleasant to drive. Had no problem with either of then (even with the dreaded 6.0 engine) but only got to about 75k miles with each: the first one was stolen and the second one I sold when I got rid of the 5ver.
Have a 2013 F550 that is my snow plow truck. Great working rig. The cab and the seats make for as decent a ride as a heavily-sprung truck like this can have (which ain't that decent :) ) No problems with the truck. (We won't talk about the plow ram gaskets)
Were I buying a dually, I would likely only look at Ford: while it's not the same truck, my current (2009 MY) GMC 2500HD has had continual problems after 100k miles with electronics and sensors (engine and tranny seem fine) and, anecdotally only, my BIL has had a raft of problems with his 2010 MY 3500 Ram.
