The thicker tangs for insertion into the stays on a forged dropout allow a stronger and more elegant looking brazed connection of stays to the dropout. On some frames using stamped dropouts, the builder would resort to flattening the ends of the stays in order to avoid thick fillets of brazing material.

I believe the brand of dropout can also make a difference in strength. I recall a biking friend who bought a new Lotus bike high-end road bike in about 1981 or 1982. Soon afterwards, one of the dropouts cracked near its connection with the chainstay. Fortunately, the importer and dealer replaced the frame under warranty.