History is history. Every GM diesel engine had it weak points which is why they have changed every couple years over the past decade. All the diesel trucks had a lot more reliability problems than their gas powered equivalents up through 2010. All three are dramatically improved since that year.
The JD Powers award for the most trouble free pickups has for five years in a row gone to Toyota and the Toyota vehicles have the most American made content of any trucks except the Ford F-150 with which they are tied. Unfortunately Toyota does not sell a 1-ton diesel powered truck in the USA.
All the companies want bragging rights which is why Ford even goes so far as to include F-450 sales with its F-250 and F-350 trucks to boost the number of units sold each year. The F-150 is the top selling 1500 class truck but it is the Ram 2500/3500 that are the best selling in this segment and the units are greater than for Ford and GM/Chevy combined. Another trick I have seen is where Ford compares its numbers to Chevy but leaves out the GM trucks from the tally.
Numbers from an automotive marketing department are as credible as those from the pentagon. They are all spin doctors.
For vehicle reliability I use the Consumer Reports data that is aggregated from all their subscribers who fill out a survey for each vehicle they own and report repairs needed during the prior year. For trucks I use a survey of repair shops that also report repairs by type and make and model year across the country. Both are far better than a sampling of a few dozen car or truck owners.