Which is better GM Duramax diesel or Cummins Dodge. What are some opinions?

It depends on what you're asking they are better about. the Duramax is cheaper to upgrade and has better fuel mileage and stock the Duramax triumphs over the Cummins in torque and horse power. but there is a lot of stuff you can do to them both but the Duramax is all around less expensive. and as to which one lasts longer that can vary, the Duramax has proven to be a very reliable engine but the Cummins also has one heck of a reputation.

Cummins= 350hp, 650 ftp of torque

Duramax=365hp, 660 ftp of torque