I have a relative who just completed his second tour as a Marine in Afganistan. He carried the Barret .50 and said it was not accurate enough.
IIRC, he had praise for the .338 Lapua. Even Savage now chambers a rifle that is very reasonably priced in that caliber.
I don’t own either, so I don’t have a review.
I’m the proud owner of a .34 Weatherby Magnum and I have to say it’s one of the most accurate guns I’ve ever fired. I’ve heard about the Lapua .338 and would love a head to head match with it.