Re: 280 rem vs 284 win?
In terms of velocity and barrel life, they will be similar as they have similar case capacities. If I had to choose between the two, I would lean towards the 284win because you can get Lapua brass. (this from a guy that has a 280rem)
What is your intended use? that can have a large bearing on caliber choice.
I'm not gonna shoot here. I'm gonna shoot waaaaaaaay over there!