With a Cummins is irrelevant. I would not own a truck without the limited slip diff (anti spin diff
Don’t even consider buying a truck ( any engine ) without the anti spin rear axle. I won’t own one without it. I also get 4WD.
With the anti spin axle it will give you both rear wheels power in slipping conditions, as opposed to just to 1 wheel. In 4WD with the anti spin axle you will have 1 front wheel and both rear wheels pulling in mud, snow, ice etc. Actually you can lock the rear and front axle to get all wheels pulling on the power wagon. The only negative that I can think of with the rear anti spin axle is when you are accelerating around a sharp turn on slick roads sometimes the back end of the truck can slide out due to both wheels spinning ( “breaking the back end loose”), where a non anti spin axle won’t break loose. That is a non event.... just get off accelerator momentarily. I truly don’t understand why they make and sell 4WD trucks without a anti spin or rear locker axle!