Boatman:
1 - the 642, like all Smith & Wesson revolvers, has been updated from time to time. Every since they started using model numbers (about 1957, IIRC), when they update a model, they -1, -2, to differentiate between the updates. The 642-1 and -2 are +p capable, the 642 no dash will not thank you long term for +p.
2- The 642-2 has a keyed integral lock that prevents firing, but allows the gun to be loaded and unloaded normally. Some people don't like that lock, nor the fact that, currently, the gun is not available without it.
3- there are many, many different grips available. If you like the one with the lazer, great. Nobody else can pick your grip for you, since nobody else has your hand to use to pick it out with. If I were new to the snubby, and got a lazer grip, I would not shoot it with the lazer until I could hit reliably without it. Then I would learn the lazer and use it for low light shooting. My gun does not have a lazer. I use a flashlight instead.
4 - The 642 has a stainless steel cylinder and barrel, and aluminum alloy frame. Other models of S&W revolvers in the same frame size have titanium replacing some or all of the steel in some of those parts, to save weight. They'll kick harder and are much more expensive. I would not get one, but instead stick with the 640 (all steel, more weight) or 642.
5 - I use a Galco pocket holster, a Smartcarry deep concealment holster, and sometimes an Uncle Mike's pocket holster. I do not use a belt holster with this gun.