I'll be asking myself a similar question when I go on my first caribou hunt, hopefully in the next few years. I'm hunting moose this year but want to also go after Sitka blacktail and caribou in the next 5 or 6 years.
I'll be debating between my 264 win mag or my 300 win mag. Both will work but I'll likely end up taking the 300 win mag. The primary reason is my buddy that I'll be going with also shoots a 300 win mag with a 180gr Accubond. If for some reason one of us has an ammo or gun issue, the other's loads will shoot fine inside 300yds in the remaining rifle. He shoots 2 grains less of the same powder and has a little longer seating depth, but his bullets cycle fine through my magazine and hit just low of my groups. My bullets are close to as good through his gun. There is a 175fps difference at the muzzle but it doesn't amount to much at normal range.
My 264 I'd consider taking I currently shoot the 140gr Berger VLD through. I used to shoot the 140gr Accubond through that rifle and it shot well also. For that trip I'd likely switch back to that load. I'd trust the Berger on a caribou, but if I encountered a bear I'd just feel a little safer having the deeper penetrating Noslers loaded up. It would just be a bit more peace of mind for me.
Definitely overthinking it as Brwnbr said, but when it's not hunting season we need something to do!