I love the Ruger for its ruggedness, plus, the grip is pretty nice, too. However, the triggers are just terrible. The S&W is a much smoother gun, and much better for your wife. Of course, you can get a trigger job on the Ruger, but you have to be really careful. Some jerks will just cut off a couple of coils from the hammer spring and call it a trigger job.
The 686 is one of the finest .357 revolvers ever made. Second only to the Colt Python in my opinion. The 2.5" 686 is about the best balanced gun I have ever handled. I started out a Ruger man, and I own several, however, once I "discovered" S&W revolvers, there was no turning back.
If she is going to primarily shoot .38/.38+P ammo, you might also look for a S&W K-frame. They are a bit lighter, and would be easier for her to handle. (Blued models, 13 & 19, stainless models 65, & 66.) These still handle .357 loads as well, so don't turn down a good deal on one of these if the opportunity arises.
I'm really glad you are getting a revolver. Some guys are just convinced the wife has to get what HE wants, and she ends up with a gun she cannot shoot well. Wise choice.