My last truck was a 2007 LBZ duramax dually. The only issue worth noting was water pump replacement at 186K. I traded the 07 in with 300K for my 2019 Dually.
Reliability and the solid track record of the Duramax Allison combo is what led me to buy another Chevy.
Honestly the other 2 have solid products, I considered both of them.
But in the end features and gadgets gave way to plain old trusted proven reliability.
I considered waiting and getting a 2020, but I prefer to buy the last year of a production cycle vs. the 1st year of a model run.
Again its all about reliability. My 2019 now has 20K miles so far zero issues.