Not true,..over the counter ammo availability for .308 offers much more in the way of high performance,..bench loaders can even squeeze more out with any of the newer performance rifles.
Fuel injection,..better acclimates to elevation changes,..and just better performance for stock vehicles.
Cold start warm ups
Or
Not
Personally,...300blk,.. Heavier projectiles give it the edge in down range performance..the only disadvantage for some is the ammo is not as readily available as 5.56.