The 7/08 doesn't have any more "punch" than the 270, and is NOT flatter shooting than the 308 or 30-06. Well, with the right bullet it could be slightly flatter shooting than the 308, but not any significant amount. And definitely not flatter shooting than the 30-06. That's impossible, the 30-06 is a longer case with more powder capacity, which translates into more velocity.
The 7mm-8 is a higher caliber (granted not a ton) so it does had a slight amount more "stopping power" then a .270. If the guy is a new shooter, flinching and the like will cause him to be significantly less accurate with the higher kicking .308 which has little gains over a 7m-08. This is even more apparent in a 30.06 although the fps gain is more extreme.
I was shooting my 30.06 with 180 gr (yes i understand it is a bigger bullet, but isn;t that the real advantage of an .06?) at a velocity of 2700 at 100 yards which is reduced to 1726 at 400 yds. With my -08 I shoot 2850 at 100 and 2170 at 400 yards.
I know that personally, I am less likely to flinch and have been incredibly more accurate, out to longer distances, with a 7mm-08 then a 30.06. Each person will have their own preference and results. But this is my experience
I don't totally disagree with everything you are saying, but it's just totally wrong to say a 7/08 beats a 30/06 or a 270. And it's so close to a 308 that there is virtually no difference. If you want less recoil and a little flatter shooting in a 30-06, use a 150 or 165 grain bullet. You don't need a 180 grain bullet. As highcountry said, the slight difference in diameter between a 270 and a 7mm isn't enough to matter (.277 versus .284) and you'll have a tough time beating the velocity of a 270 with a 7/08, although it won't be too far off.
The point is there just isn't as much difference between cartridges as you seem to think. The bullet you use in each particular cartridge is what makes the difference.