S&W eliminated pinning their barrels as a production change. This production change is reflected in the newer dashes (-).
S&W eliminated pinning ther barrels because not pinning them meant two or more process could be stopped, making production faster. Taking out the pin does not mean the unpinned barrels are stronger, or weaker. Nothing really changed. Think of it like wheel nut lugs. Five lugs used to be the standard on most light to medium cars. The standard is now four with no weakness without the 5th.