I know there are those who will disagree, but I see no advantage unless you want to shoot suppressed. And for a lot of guys that is good enough reason to own one. The 300 Blackout isn't capable for any game larger than deer regardless of the bullet it uses. The 5.56 or 223 with the heavier 60-77 gr bullets is at least as effective on deer sized game, and better in my opinion. Those heavier 223 bullets will be still be fast enough to reliably expand and still give plenty of penetration out to 200 yards. Probably with complete pass throughs on deer size game.
Most .308 bullets are designed with 308-300 magnum speeds, not 300 Blackout speeds. The heavier (180 gr+) 300 Blackout bullets will be too slow to reliably expand in game even at the muzzle. Bullets in the 150 gr range are fast enough to ensure expansion for about 100 yards or so, beyond that even they are too slow. I think the 125 gr weight is the one with the most potential in the 300, but don't see it offering any advantage over a 60-70 gr 223.