2016 frieghtliner cascadia. Short nose. No where near the pick up of the dd15. But just as much power just takes a little longer to get up to speed. If you run west of the east cost to mo. It will treat you right.
Biggest problem so far is having to rotate the drives every 38 to 42k. Miles because of the single drive axle.
Not all dd13s are Single drive axles with a dummy axle thou.
If you need that pick up. Get the 15. If 70 is 70 no matter when you get to it. Grab the 13