They have more balls with skinny rear tires and stay in ruts better, I dont like 12 wide rear tires on an irs atv.
You can run 28x10's front and rear on stock rims no problem. My brother has 28x10 wild thangs on stock rims on his 21 rubicon dct. I have 27x9's front and rear on stock rims on my foot shift rubicon.
My brother had 27x9's front and 27x12's rear for a while but mine had quite a bit more power with the skinny rears and rode nicer so he switched to 28x10's, even tho the tires are taller it has more balls as they're lighter and skinnier.
The exception to all skinnies is zillas or wild thangs, the 11's are only 10 wide. If you get zillas get 27x9's and 27x11's.