This is highly personal, like why you chose the one you married. 😮🙂

But used the 340 Wby for a quarter century and very successfully. Of some 12 bulls and a caribou bull I only needed a second shot, and it wasn’t really needed.

The 340 and 338L are essentially ballistic equals. The 300 Win is a good cartridge. I have no experience with the Nosler and 280AI but do with the 284 Win which is just a step behind the AI. If the magnums are not necessary for elk, they will definitely do the job if you can handle them.

Are you a hand loader— another factor to consider.

If you are a hunter meaning not sending multiple hundreds of rounds down range a year you will not burn out a good barrel in years if ever in your hunting lifetime.

I would forget the “recoil arrestor” or at least, have a removable one. No Magna-Porting of the barrel or anything like that or you’ll likely regret it.