Explaining how the .308 is better for deer in brush than a .270 is like trying to explain why soldiers liked the .30 Carbine better than the .223 for jungle warfare in Viet Nam, it's complicated to some, yet it works.

The problem with smaller bullets with higher velocities, is that at close range,well, they have high velocities, and they don't always expand as well as larger bullets do.

Shooting at a thick board of wood at the shooting range with my dad, I was using my .308, and he was using his 7mm Rem Mag, and no doubt, 7mm Rem Mag has got more downrange power and velocity, but when we were shooting the board, my bullets expanded better than his, his would pass through alright, but didn't expand as well, since there wasn't enough time for expansion, it just zipped through, because the 7mm has smaller diameter, and goes through faster, it's like seeing, which item would penetrate the piece of paper better, with a biggerhole and damage, a pencil, or a toothpick?
It's like that, so for close range, that is one reason I would choose the .308 over the .270.