Been hunting with a 7.62x39 for 15 years and killed a lot of deer with $2.00/box Wolf HP (still have some). Upgrading this year to LR308 just because I want to. Most shots are under 75 yds, so it really doesn't matter what we use.
In an AR15 platform, the best round for hunting that I'm aware of is the 25 WSSM. 25-06 performance in a case short enough for the AR15 receiver. The only problem is finding ammo.