It's all good Steve, you're right in terms of practical purposes. A 165 grain would probably be the best all around 30-06 hunting bullet. That would be ranges out to 500ish yards. But to really stretch the capabilities of any cartridge, heavy high BC bullets is the answer, IF it can be stabilized...
About a year ago I messaged MontanaMarine. Shane gave me some good start loads with these heavy bullets, and I was able to get safe loads to 2600 fps. I actually went to 2700 fps but accuracy was better at 2600. He has taken these bullets to a mile in a 10 twist 30-06, with great results.
So.... In my opinion if the ballistics are similar to 600 yards, between the 165 and 215. The 215 starts to pull ahead after that so it would be the more efficient bullet. The 215 has a lot less drift, and more energy across all distances compared to the 168 Berger VLD. And it has more or as much energy at 1000 yards as the 168 does at 650 yards...