The Cummins is the best engine for pulling, but the Allison transmission in the GM trucks is far superior to what the other two offer, and the Duramax is a good engine as well. Other than that, I prefer the looks, ride and over all comfort of the GM. Fords, I don't/wouldn't even consider.
Becky, Bob and Taylie & Bode
2009 Silverado 2500HD Duramax/Allison
2014 Heartland Sundance XLT 245RL