Ok, so I think what you`re saying is the following :
The main advantage of squaretop over pinhead sails is that the airflow over a squaretop sail is more laminar (a pinhead will always have wind going up the leech, trying to find shortest distance.)
HOWEVER : If you are slightly oversheeted on a squaretop sail, the drag is higher than on a pinhead, since the pressurised air "jumps over" the head, causing a lot more drag. Am I right in assuming that a pinhead sail would be a bit more forgiving in this regard, since the air has no head to hook over, or would it be even worse as the air is already travelling up the leech to a certain extent ?
If my assumption is correct then correct settings while sailing with a squaretop is more critical than a pinhead sail.
??
Steve