260 Rem or 7mm-08 flip a coin.
There are some very cool riflemen (routinely making good shots on game) out there that kill regularly with what many (including me) would consider marginal calibers. But probably more important than caliber (if a reasonable caliber is used) is the construction of the bullet.
I, for one, would not recommend marginal calibers for everyone, even if Jack O'Connor or any other shooting expert used it. A friend in AZ was stating that he was proud because he drew blood (did not find the elk cow). He followed the blood trail for a full day. I was ashamed for him - mostly for bragging what he did. Maybe he was a poor shot, but the rifle/bullet he was using was marginal in my opinion. Another example, my brother-in-law shot an elk with a 165 grain Sierra bullet in the lungs - the cartridge 300 Win Mag. He chased that elk for all that day following a lung blood trail. He never found that cow. My guess he might of ruined one lung and the bullet didn't make it to the other. Certainly a 300 Win Mag is more than sufficient for elk.
I'm in my middle 60's and shooting a 338 Win Mag is still my first go-to rifle for elk. But for some the 338 may not be the best. I aim for the opposite shoulder or the heart depending on the angle of the shot and desire the bullet to go all the way through. I like blood trails that are short and I hate to see an elk run down a ravine when I'm the one carrying out the meat, hide and antlers. Maybe when I get old I'll have the luxury to have horses to haul these items out...
I'd say that to each his own. My recommendation is if you can hit a 1/2 size pie plate every time at the maximum range your going to hunt, use the best caliber and bullet combination you can get a hold of. One wasted elk in a life time is one too many.
