The .300 win mag is more than capable of 1000 yards and it stabilizes far quicker than the .338 . I have a buddy that complained about his savage only shooting 4" groups at 250 yards . He did not know that the .338 doesnt stabilize well until out past 400+ . He sold it and bought a .308 as that will take care of his 500 yard max . Either way both rounds are going to rock you pretty well
Either the .300 Win Mag or the .308 seems like a much more logical choice for price of ammo considerations. I don't have a place to shoot past 300 yards and my $.35 .30-06 reloads do the job fine. I can't see paying $5 per shot or even $1.50 per reload.