Smith, advantages: Nicer trigger, and nicer revolvers in general than rugers.
Ruger advantages: Unparalled durability for withstanding a lifetime of hot loads. the "investment casting" allows a design that does not require sideplates, whose screws can back out. Their cylinder has a three point lock up design, you're not going to find a gp out of time.
But if you are really going to conceal a revolver, you might want to reconsider the 3" option, or reconsider an auto (GLOCK is "point and click" also, and your whole family can shoot for example a 17).
That being said, your first instinct is a solid one; the GP100. If you want four inch, adj sights, durable revolver for range and hd, that will outlast you, you can't go wrong with a GP100. I had a SS one configured exactly like this, within a few hundred rounds the trigger was even much more slick. Though I eventually sold it to someone (here on THR in fact) and bought a GLOCK.