Let me try to do a better job of addressing the individual parts of OP's query, which was
In a S&W 686+ 6", is it too loud or too much recoil to use effectively in a self defense situation? Would the noise and blast make you hesitate more between shots?
I'll take the second question first: I do not think that the noise and blast would make me hesitate for between shots, and while I have no reason to believe that it would to so in others. But I cannot speak for others.
Let's break the first question into two parts:
- ...is it too loud...to use effectively for self defense?
- ...or too much recoil to use effectively for self defense?
The answer to the first part is "no", and the answer to the second part is probably no, depending upon loads used, as pointed out by Webleymkv, and considering that the OP is speaking specifically of a 6" L-Frame. But effectiveness is a matter of degree, and in a situation in which more than six rapid shots may be required, say in the case of more than one fast moving attacker, that revolver would be less effective than other choices.
The fact that a .357 Magnum with robust magnum loads is a very poor choice for self defense unless some very robust hearing protection is used is indisputable. And the .357 Magnum is by no means alone in that regard. The reason has to do with the sound pressure generated by firing such a weapon indoors, and the permanent physiological damage that that sound pressure can cause.
This post from some time back contains some very relevant objective data that compare the relative sound pressured of some different noise sources.
One will note that the .357 listed (doesn't specify which one or which load) generates more than four times the sound pressure of a .45 ACP and somewhere between three and four times that of a 9MM. A 12ga shotgun with a barrel length of 18 inches is way up there too--about half the sound pressure of the .357, but two to three times that of a .45.
This, which discusses the effects of reflection in a closed structure, is worth reflecting upon.
I take this seriously. I suffer from severe permanent noise-induced hearing loss in one ear, caused primarily by firing high-pwered rifles without hearing protection about ten times (range sessions) a year for around five or six years. My hearing aids cost over $7000. As it happens, I studied the subject of noise induced hearing loss in an engineering course in college. The primary causes most often encountered in those days were industrial ( that included agricultural and aircraft operations causes) and firearms-related, but today, loud music is the biggest cause.
If I had a 6" 686, I would not hesitate to use it for home defense,
with carefully selected (read: lower pressure) loads and with
good electronic muffs.
I do not own one because my HD firearms also serve for concealed carry.
I would not select a small lightweight .357 Magnum for general CCW. Noise would be
one reason, since I do carry my CCW firearm indoors, but the primary reason would be my inability to get as many hits as quickly on a target as I can with a lighter recoiling semi auto, and still have a couple of rounds left over.
For carrying on the trail, the .357 Magnum would be my first choice.