I have the dual 125 amp alternators on my 2011 Chevy diesel. They were on the truck as ordered by the dealer. It was a $270 option on the window sticker. Not sure it is/was a real need for me but so far, 20,000 miles it has been trouble free and sure recharges the truck camper battery quickly when I start driving in the mornings. I used an extra heavy gauge wire when I wired the truck camper to the truck alternator system. I probably wouldn't order the dual set up, if I had the choice, but I would sure compare the cost of the dual system to just getting a larger single alternator.
My last truck, a 2002 Dodge Cummins diesel, worked fine for 144,000 miles, with a 95 Amp unit as I remember it being. Most of those miles were either hauling our TC or pulling our 5th wheel.
When the dealer ordered the truck we ended up buying, I think they added just about ever option available. Sometimes though to get an option you want, you have to order a "package" of options. So I also have electric seat heaters, a very valuable item to have in south Florida. LOL I found it interesting that in the past, getting a 4WD was a separate option, but on our Chevy, it was included as standard on the Silverado 4WD model, making it difficult to figure out just how much I paid for the 4WD. Part of their marketing I would guess.