I am thinking that your question is a variation of "Which 357 mag revolver should I buy?" If you can only have one, then it is hard to beat a 686. That's on S&W's L frame. I happen to like stainless but if you prefer blue than you can get a 586. For general range shooting, or a bedside gun for home defense than a 4 inch barrel will probably make you happiest but depending on your preferences you could also choose 3 or 6 inch. To me a 2.5 inch 686 is too big to consider for concealed carry, but there are guys on here that say they do.
If CC is your plan, than imho you would be better off with a J frame. Just be aware that the smaller lighter J frame isn't going to be as pleasant to shoot 357 mag cartridges though than the L frame. Most people who CC J frames choose to use 38 special or 38 spec +P cartridges. I believe these cartridges are fine in close range, self defense situations (depending on bullet type) but you will find people who will tell you anything less than 45 ACP or even 12 guage 00 buckshot is inadequate. Be aware that the steel frame J's are going to be a bit nicer to shoot, but the aluminum or scandium J's are going to be nicer to carry since they are much lighter. You can choose concealed hammer, like a 640, shrouded hammer, like a 649, or exposed hammer, like a 60 depending on your preference.
S&W makes some dandy N frame 357 mag revolvers, for example the 627. The advantage with these is you can get them with 8 shot cylinders. Personally, I am still trying to find the right grip for my N frames so I get my index finger placement where I want it. I am finding I prefer the size of L frames (which offer 7 shot cylinders) even though I wear Mens large size gloves.
Hope this helps you choose. What ever you choose, you will love but there are so many variations you will probably want to get more. Good luck!
