I had the same questions as you when I built my custom 338 Lapua. I got the rifle and shot a couple hundred rounds through it. Rifle shoots fantastic but I decided I wanted a little more. I sent the rifle back to my smith (Joe Starns) and had him put a 30" Lilja, #8 contour, 1-10 twist, chambered for 338 Lapua Improved.
I will have the option of switching barrels if I decide I want to go back to the 338 Lapua but see no reason for doing so at this time.
All said and done, I should have ordered one of Kirby's big magnums in the 1st place and been done with it