I am a huge fan of 30-06 for whitetail, but I'd be the first to say it is a bit overkill. Overkill is a good thing. If it was one of those "1-Gun Deer Battery Threads" that would be my choice.
If you're looking for the best, my nomination is the 300 Savage. Why not the 30-06? Here is my reasoning.
Most whitetail deer taken by most hunters are taken within 80 yards. At 80 yards, the 300 Savage is just starting to differentiate itself from close-in deer chamberings like the 44 Mag and 30-30. 300 Savage puts them down about as well as you can manage without a lot of recoil-- much less than 30-06
I've got 3 kinds of hunting venues at the farm. When I'm down pounding the ground in cedar thickets, I'm not too worried. Nearly everything works. My all-time favorite for that kind of work has been the 12 GA slug. However, my recently-acquired 44 Mag semi might take that slot. Ditto for my deep woods blinds and stands. At the other end of the spectrum are the few venues that offer a shot more than 200 yards. When I'm out hunting there, I normally carry my 30-06 or 8X57 Mauser. Previously, I also carried my 35 Whelen, but it's honestly too much thunder for too little additional gain.
300 Savage (actually mine is a downloaded 308 WIN) is perfect for in the middle. I have a stand that overlooks where two creeks come together on one side and a hole in the fence leading out into a narrow pasture on the other. Most shots I've taken have been well within 80 yards. Some have been right at the ladder, but occasionally a buck will appear out in the field and I may shoot 150 yards to get there. I have another venue that is midway through a pasture. It is 150+ yards looking one direction and 180 yards going the opposite way. Again the 300 Savage is ideal for that sort of venue. The 300 Savage specs fit right in the sweet spot where I'm most likely to encounter most of my deer.
As a runner up, I would nominate 7mm-08 or 7X57. I don't own one but it is on my bucket list. I've already retired my 35 Whelen from the rotation; it was my high-water mark on recoil. When I get old and wretched enough to want to retire my '06's , I'll start whacking them with 7's.
