Hey Amigo,
Before owning the Bren, I've never had 3 point slings and thought they were just an unnecessary complication. However, because of the weight of this firearm, the second point of attachment helps in limiting the movement (sliding) or see-sawing of the firearm once slung on your body (that was difficult to describe). For this reason, the OEM 3 point sling can be useful. Of course, there are disadvantages to a three point sling.....shifting the firearm quickly from right to left shooting positions can be cumbersome.