We had this discussion before but in my opinion, there really isn't a dusty spit's worth of difference between them. As Brit points out, the 30 caliber will have a greater S.D. than a comparable weight bullet in the 8mm but who cares? Either would be lethal. One aspect of the 8mm is that some European loaders load to smewhat higher pressure levels than the 50K pressures that the 30-06 is held to. Int he US however, they are deliberately and woefully underloaded, with undersized bullets, to keep the ammo makers out of court when some fool with a 1888 Commission Mauser with a .318" groove diameter shoots a standard 8x57 round in his rifle. These are again, two old rounds that are held to somewhat subdued pressures in deference to the weaker arms that they were once chambered for.
As to the 8mm-06. Well, the advent of this wildcat had nothing to do with efficiency, and more to do with practicality. When loads of surplus 8x57's were being imported into the US, shooters wanted a more readily available case, or one more "powerful" (remember the downloading of the 8x57 here...) for big game hunting. The 8mm-06 filled that requirement nicely and was an easy conversion: it was a simple reaming job for the gunsmith. (I have made many of them in the past) The only problem with such a conversion was that the magazine usually ended up a bit short and if the conversion was done correctly, the magazine would need to be lengthened. In the case of my Winchester Model 1895, it is again, an expedient. The bore is dark and rough from mercuric priming. I would rather it remain a 30-06 if it had a bright, servicable bore, but it doesn't. An 8mm-06 is the logical choice. A "35-06" would be a hazard as that constitutes a 35 Whelen... a round that would definitely be dangerous in such a weak action.~Muir