In 2015 I test drove a Chevy 3500 6.0 and a RAM 2500 6.4 back to back. The RAM had much snappier acceleration for sure. It felt more like a sports car compared to the Chevy. It may be that Chevy has a lot of torque management in the computer. For various reasons we ended up purchasing the Chevy. It's a work truck with a tool bed and ladder racks on it now. I've got 41,000 miles on it. All of it hauling, some of it towing. The truck weighs 9,000 pounds on it's own. I had 10,000 pounds of trailer and blocks behind it and it was almost effortless. Towing the same 4,000 pound trailer loaded with a 9,000 pound excavator was the most I've had behind it. It was going up the mountain at 35 MPH with my foot on the floor but it did it and didn't get hot.
I have no regrets. I don't know if the RAM 6.4 would have been better or not.