Not so fast there Bubba, there are many people who would say that adjustable sights have no place on a snubby. For those people, the drilled & tapped top strap give you the option of easily replacing the rear sight with a C&S fixed unit, like S&W did on the Night Guard series.
Also - the old style, square-tang, rear sight (as on the -3) is no longer available from Smith, so if you damage the rear sight you are SOL unless you can find one in nthe secondary market. Right now those prices are all over the board, but seem to be trending toward about $130.
I would prefer a -4, but that's just me.
Adios,
Pizza Bob