Accuracy difference between the two is hard to quantify.... the particular rifle, the particular load and of course the shooter....
It's been my experience that generally speaking the 25-06 tends to be a bit more accurate with everything else being equal.
However, I've seen a few 270s that were like lasers. But not many.... more often the 25 is gonna be the winner in a accuracy contest.
As to brands.... I've only had one Savage that didn't shoot like a house afire... and I've owned dozens of them. They're one ugly rifle but they usually perform better than rifles that cost 3 and 4 times as much.
I've seen Remingtons that shot great and a bunch that shot like crap. I've had maybe 2 dozen Rugers, all shot acceptable groups for killing deer except the Mini 14 I had...... what a pig that was. Most of the Rugers were mediocre though....average at best.
The best shooting Ruger I ever had was a early 80s M77 in 300WM..... that thing would put 2 shots into .6 or .7 like religion..... never should have sold that one.
Had a bunch of Winchesters too, some good most average and a few pigs. Same with CZ, SAKO (way over rated in my opinion) and Weatherby...
Had a couple of Tikka's.... they were ok as well. But nothing to brag about.
Several Browning A-Bolts.... I was happy with most of them but the only really good one was a stainless 308 with the BOSS.... that thing shot great but the noise ran all my friends off....... had to sell it