The advantage is just sling placement options as said before. Although both are very obsolete stocks compared to offerings from LMT, Vltor, and Magpul as they allow swivel joints on the sides. Side swivels are superior when using a good two-point sling such as the Vickers VTAC. Combat troops and other people who walk more than they shoot have little use for the single cotton web slings and leather hi power slings that are mounted on the bottom axis of the rifle.
I've seen quite a number of troops who use the stock sans the bottom sling mount for use with thick body armor or vests. Plus a car seatbelt through the top of the stock hooked with the front works ok in a pinch.