Hand loaded 165 Nosler Partition @ 2,750 ft/sec muzzle velocity. Accurate (in my rifles), opens up like it needs to (at least on actual 30 to 175 yard shots on ten "normal" sized whitetails), and I'd like to think that it would still create a substantial exit wound even on a quartering shot on a really big buck.
That being said, standard factory ammo is probably just fine for 95% of all shots taken on whitetails. in my opinion, shot placement is WAY more important than projectile type with a definitely powerful enough round like the ought-six.
I am also considering the new Federal Fusion ammo, supposedly bonded core bullets that are designed to open up on whitetails. They shoot reasonably well in my rifles, but I haven't yet seen any field reports on how well they work.
Best of luck to you.