Dude, between those two, it doesn't even make sense to get the lower option. Look closely at the barrels. They are both lw profile under the handguards where most of the bending or flexing will occur. Then it gets wide again, in front of the gas block. Sure a little weight in front will help tame muzzle rise a bit, but it also make the gun heavier in the worst possible place, making it harder to swing, steady and carry.
I think another difference is that the gas block on the pencil profile is .625, and the other is .750. It doesn't matter, short of a jack hammer you not getting a BCM pinned gas block off.
Get the pencil profile. You won't regret it.