[Notanlines]

I can only speak about the Ford F350/F450 and the difference in radius. It was the selling point that made my DW come to the F450, and she loves it over or older F350. It is considerably easier to maneuver everywhere.
You might also keep in mind that most truck manufacturers de-tune the 4504500/5500 commercial diesels (those with no bed) for product longevity. Don't talk to your salesman about this: He/she simply won't know. Do your own investigating. Your Cummins in the 5500 is probably a 800 torque/360 HP engine.