I asked a friend about the age old 270 vs 30-06 debate a year or so ago. Here was his response.
“That is a tough one, but I will give you my personal assessment. I have been using both since the mid 90's. At first, I used the two mixed in with several 7mm and 300 mags, but have hunted almost exclusively with a 270 or 30-06 since 2008.
The 30-06 has a much better selection of bullets available, both in factory loads and component bullets. You can find almost any bullet you could possibly conceive from lightweight varmint bullets to 250 grain Woodleighs. The 1-10' or 1-11" twist you find in most 30-06's will stabilize most of them. I think this is due to the fact that 220's were a fairly common load from the early days of the 30-06.
Like all older cartridges, new powders have given the 30-06 velocities that were unheard of 20 years ago. 150's at 3100 or so, 165's around 2950-3000, 180's around 2850 and 200's at 2750 are all easy to achieve. At that point, it is pretty hard to say a 270 has any real world advantage. I doubt a hunter would notice much difference in a 150 grain 30 caliber bullet at 3100 or a 130 grain 270 caliber bullet at 3100, without getting too gacky. about SD or frontal area.
Last summer I spent some time with my new 30-06 loaded with the 212 ELDX and R26. I was able to get 2750 without any effort at all and the cases have been fired 8-10 times and are still trucking along. That brings up another point, that Lapua brass is readily available for the 30-06, if a guy likes Lapua brass. The 270 has a smaller selection of better quality brass. I recently got 100 pieces of RWS 270 brass. I paid more than Lapua and while good, it is not as consistent as the Lapua.
As far as effect on game goes.....I have not been able to discern any difference on sheep and deer sized game. Both will kill with more power than is necessary. In my experience, I think I have seen more 'effect, or impact, or reaction to the shot' or whatever you like to call it with a 30-06 on animals starting with grizzly, caribou, and elk sized stuff. It may be a mental thing, but I would rather carry a bloody pack full of caribou meat through the alders with a 30-06 loaded with .308, 220 grain Partitions (or whatnot) than .277, 160 grain Partitions.
I will probably always have a 270, as I am a far gone O'Connor fan, and my wife likes to shoot my 270 due to the slightly lower recoil with 130's. Having said that, I have spent hundreds of hours with Brad O'Connor over the years, including staying at his house multiple times, and he claims Jack would always say the 30-06 was a more versatile all around cartridge. He will then point out that while he always had a 270 available while hunting in Canada, that something like 11 of Jacks 12 grizzlies were taken with the 30-06's he also had along on the trips.
Another guy I know, who is a dyed in the wool 270 guy, goes to Africa every year on high volume plains game hunts. He sees literally dozens and dozens of animals taken every year, from impala to eland. Multiple times in the last few years he has told me that while he still loves his 270's, he has found the 30-06 to be a little better on the bigger plains game. And as John Oosthuizen once told me, if you run out of 30-06 ammo, just look under the floormats in the Land Cruiser….there will be some there.”