One for my Family...medium
One for my wife's ...medium rare
I prefer medium rare.
Cooked in Smoker at 225, until internal reaches (115-120 for med rare. 125 for med). Takes about 3 to 3.5 hours, then reverse sear on each side about 2 mins for a nice crust. This is as good or better than anything you get at the restaurant.
Btw, at my Costco you can get choice or prime graded meat. For the prime rib, since you are smoking low-slow, I cant notice a difference in taste. I dont think it is worth spending the extra money.
Grilling, broiling, or pan searing is a different story though.