New superwinch hubs are not much over 100 bucks. Takes less than 20 min to install each one. They have a lifetime warranty, I broke one in the first month or so (aftermarket CV exploded and pushed the Hub guts out) They sent me two brand new ones!!!! Now I have a spare, ZERO cost to me. I just had to mail the old one back, so I guess 8bucks S&H.
From an efficiency standpoint, there has to be some energy lost in spinning two extra tires, as well as load on the front drivetrain. As it has been said countless times before, they will be spinning, but not under load. I found that my acceleration seemed to improve, and my steering felt "lighter". Not sure how to describe it any other way, maybe it was all psychological? But if you bust a CV on the trail, as crotch mentioned, they are a life saver!!!