I don't know anyone with a third gen Cummins that has had any injector problems. I have almost 30,000 and have not had one problem with the engine.
I had a Duramax for three years. 72,000 miles... lost a head gasket. No injector problems but I simply do not trust the Dmax for over 100,000 miles as a personal vehicle. The costs to repair are scary. Yes they are high with the Cummins or PSD but I like my chances better with the Dodge. I don't think you can go wrong.
Check out the GM diesel sites and read the signatures closely. Very few keep their truck over 100,000 miles. Yes they are nice if you don't mind trading often. Also do a search on injector problems. They have major injector issues.