Having shot dozens of deer with both the .243 and 100 gr Hornady Interlockbullets (40.5 gr of IMR4350) and a .270 Win with 130 gr Nosler Ballistic Tips (55 gr of IMR4350) and a few with the 7-08 (the load escapes me right now but with 139 gr Hornady Interlocks, and as much as I like the .243 and its effectiveness, as well as the 7-08, both excellent whitetail rounds, I have to lean toward the .270 Win.
Now I'm not saying this is the 'best' whitetail round out there but a deer hit in the right spot with a 270, 280, 30-06, 7mm Mag will never know the difference.