And the .308 isn't? It's the number 1 sniper round used today. Amazingly accurate in a hunting round out to 300 yards or better. Snipers making shots out to 1200 meters with handloads. Military has been using the round for many years. I bought my first .308 this year and wish I had done it sooner. Started rifle hunting with a 30/06 in 1984 when I was 15. It's a great all around gun, but if I was try to pick between the 2, I would go with the .308 again.
As for a round that has killed more deer than any other, I would have to guess it would be the 30/30. That would be my gun to settle for if I had to give up all the rest.