When did we suddenly start talking about "ball rounds"? First, nobody hunts with FMJ .308's. Second, it seems rather crazy to think that a round with only 500 ft lbs of energy is somehow dumping more energy into an animal than a round with nearly 3000 ft lbs of energy, even though the more potent round goes "through and through."

There's quite a bit of literature on wound ballistics, and I thought that the theory that a bullet that dumps all of its energy into the target (by failing to fully penetrate) is somehow superior had been written off as myth. Read pages 5-7 of this:

http://www.firearmstactical.com/pdf/fbi-hwfe.pdf

As far as your contention that ...at 20-30 yards... "a .308 tends to overpenetrate and (in my experience) maims large game unless the shot is accurately places in a vital area," I guess I'll have to cede to your experience. At 20-30 yards, I've never had any problem "accurately placing a shot in a vital area."