"I would go for the most reliable and proven power in heavy duty towing situations. "
You don't get that from a test a Magazine does. You get that from real world experience.
The Duramax/Alison combo is good, rated at 250K but the Cummins is rated for 350K.
Think about it, all Cummins does is build engines. Less moving parts, you can see both sides of the engine, the in line 6 is the best for delivering torque.
I would pick either way before I would think about a Ford.
Take a new Ram Longhorn for a spin, that will open your eyes to what an improvement Ram has made in the last 3 years.