You are also looking at only one aspect of hitting a small target at long range and that what our goal is. Our goal is not just to hit a big game animal, its to pick out a relatively small target on that big game animal and put our bullet in that spot.
As you mentioned in your last post, reading the wind is the real challange once everything else if fine tuned.
Which again takes us back to your original question, is bigger better. We have talked a bit about terminal performance but just as important, and perhaps more importantly, hitting the target is key at long range. So is bigger always better for long range shooting. Lets see, The longer the bullet, on average, the higher the BC will be. the higher the BC, the less drop and drift you will have while the bullet is in flight all else being equal.
Now take that larger bullet with higher BC and put it on top of a larger case capacity and you can drive it faster. Given the same BC, the faster you push a bullet out of the muzzle, within reason, the less time gravity and environmental conditions have to effect that bullet in flight.
This gives the shooter a larger margin of error in judging external conditions which means you do not have to nail the conditions dead on the money to still put a bullet in the vitals of a big game animal at long range.
If you simply look at the ballistic aspect of your question, if all is equal, the larger chamberings allow us to hit small targets easier then with smaller chamberings, ESPECIALLY when the wind picks up a bit and we can not predict exactly what the wind is doing down range.
With todays advances in muzzle brakes
, there really is no reason why very large chamberings can not be shot by anyone that wants to shoot one, not only shoot, but shoot them comfortably and extremely accurately. My wife shoots my 338 Allen Magnum with amazing precision, as well as I shoot it and thats with a 300 gr SMK loaded to nearly 3400 fps. Felt recoil is probably no more then your unbraked 270 Win and certainly less then an unbraked 7mm Rem Mag.
So, if your goal is to get the rifle system that allows us to put the bullet on the mark with the most efficency possible, there is no question, the big guns can do things that smaller chamberings simply are MUCH MORE DIFFICULT to accomplish in same conditions.
I have made a living with this theory and my customers prove this same theory to themselves all the time. I also reaffirm the theory everytime I take one of my Allen Magnums or Allen Xpress wildcats out in the field and see just how easy it is to hit small targets at long range once you have your rifle, load and drops accurately figured out.
So ballistically, yes bigger is better in my opinion. In ideal shooting conditions, may not be such a huge advantage but generally conditions are FAR less them ideal when we go to the field hunting.