Discussing barrel profiles with disregard to the parent material used in the manufacturing process of the barrel is the first mistake of this discussion.

Pencil barrels have their place and can function as well as a heavy profile in MOST applications. SCAR's are a perfect example of the manufacturing process allowing a pencil profile to function like a heavy barrel. Almost. They are still inferior to a heavier profile when it comes to hanging a supressor off the end and for maintaining a consistent zero firing long repeated strings of shots.