The ballistic coefficient is the selling point. It does plenty of damage with a lower charge than other cartridges in the same ballpark. As with the 9mm vs 45 argument bullet construction has improved over the years allowing for smaller calibers to compete with the old heavy weights. For a deer round regardless of what caliber you shoot the most important thing is to only take ethical shots and you shouldn't have any escapees. If you're already in a 308 and like it I would stick to it. If you just want another caliber the 6.5 is a lot of fun in my opinion.