Gas engine and Diesel of same specs.Pull the same.

ib516 wrote:
The diesel will pull at lower rpm with much less transmission shifting. It will also get 50% better mpg towing or empty.

Lower rpm = lower road speed, unless you run in a higher gear which means lower torque at the wheel. You can't have it all unless you've got HP. I seriously doubt a stock 235hp diesel with similar torque to a 345hp gas engine would pull as well but I can't say I've had first hand experience. Modded is another story for either engine.