Number of pros to the pinned barrel, including:
1. The barrel is more likely to be aligned with the sight vertical, instead of canted left/right as is common with the crush fit barrels.
2. A lot less stress on the frame and barrel extension, espeically if the person running the machine that screws the barrel into the gun (crush fit) isn't paying attention. I've seen far too many S&W revolvers with crush fit barrels that have obvious stress rings in the barrel from being screwed in too tightly.
3. Easier to remove the barrel to replace it.
4. Easier to replace a barrel.