I prefer the .30-06 because it has so much more latitude than the .308 Win. I don't always shoot full house loads in my .30-06 bolt gun, in fact most of my loads are down around .30-30 performance. But the option is there to load up when I want or need it. I have a .308 Win chamber adapter I use in my .30-06 bolt gun for when I want to shoot .308 Wins.
I consider the .30-06 to be the smallest member of the .30 caliber magnum family. The .308 Win is not, but it is still a very powerful cartridge.
This is a bit of an arbitrary distinction, but I based my definition of the .30-06 being a magnum cartridge on its power now being equal to the original .30 Holland & Holland Magnum cartridge. The dramatic increase in power is from the use of modern powders.
The .300 Savage now has about the same power as the original .30-06 did in 1906! Savage developed that cartridge as a replacement for the .30-06 and the .308 Win was based on Savage's work back in the 1930s.
After WW2 the U.S. Military realized that a smaller cartridge could replace the .30-06 and still provide the same velocity with the same weight bullet as the original specifications called for. So the 7.62 NATO and .308 Win were born, using Savage's data as a starting point. A shorter cartridge had the advantage of having a lower bolt velocity while still provide the same rate of fire in semi-auto and full auto weapons. A lower bolt velocity causes less wear and is less subject to jamming problems.
I have one rifle that shoots the .308 Win cartridge and five that shoot the .30-06.
rl727