Some solid advice here. When I saw your thread title, a Ruger Wrangler was my 1st thought, but you already have one. I bought my 1st handgun (with Dad signing) at 16-a 6" Colt Peacemaker .22 with non adjustable sights. I ran brick after brick through that thing, and could outshoot my cousin, with him shooting a .22 rifle. Next, I bought a Mk 4 series 70 Colt Gov .45 ACP, followed by a 6" Nitex Python .357, using a single stage press to reload .357 and .45.
I know you want a revolver, and you likely considered some of these things, but here are a few things that I would be sure to consider...
Weight. A 4" 686 weighs close to 40ozs, or ~2.5 lbs. While this does mitigate recoil, It could get tiresome to all day carry. That's nearly x2 the weight of a G19 sized auto loader. If you're a big guy, this will be less important.
Revolvers (excluding snubbies) are generally more difficult to conceal.
I agree with those who've said snubbies are not beginner guns. IMHO, they are an experts back up piece.
I would not buy a first revolver that limited me to .38 Special. The .357 is far more versatile.
As your shooting progresses from single to double action, you may be surprised at how quickly a 6-7 shot handgun runs dry. I've known more than one experienced LEO that are familiar with this phenonium. When someone is shooting at you, there is a strong probability that you will stay on that trigger, and will run that wheelgun dry, sooner than expected.
Reloads: I know the pros can reload revolvers very quickly, but it requires more regular practice, than reloading an auto. Much more chance of fumbling a reload with a revolver, and speed loaders are more bulky to carry than extra mags.
If $ is a consideration, an auto may be more future proof. If you stay with shooting handguns, you'll probably buy an auto, at some point, anyway.
Finish: I learned about sweat and blued guns, with that 1st Colt Gov .45. My sweat rusted a pretty good area of the exposed slide. Yes, you can wipe it down and oil it daily, but it happened, despite my being pretty consistent with maintenance. Blued finishes are nowhere near as corrosion resistant as more modern finishes. Kydex holsters will wear through bluing quickly, and if your leather gets wet...
Sights: Don't be afraid of adjustable sights. Learning to zero irons, after learning the basics, is part of becoming proficient. Different ammo can have different POI (point of impact), and not all fixed irons shoot point of aim. Adjustable sights give you options.
SA vs DA: I agree that most SD training should be in DA, but a SA option can greatly increase hit probabilities at longer distances.
Cost: There is something to be said for carrying a less expensive piece. In the unfortunate event you must use it in SD, it could be tied up in evidence indefinitely, or permanently. As mentioned, police trade ins are a economical way to acquire a piece that has been carried much, and likely shot little. There are reasons LEO depts. haven't chosen revolvers as primary sidearms, for decades. There are also great LEO trade in deals to be had with S&W M&P and Glock pistols in 9 or .40. I prefer the M&P trigger. The only thing I would mention about the M&P is that the slide can sometimes drop on a slamming a fresh mag home, chambering a round-train accordingly. Learning proper trigger and muzzle discipline are key, no matter what you carry.
If you are looking at buying an older piece, research the various iterations of that model. There are often improvements in a given models' development (-2, -3, etc.) that can affect value significantly.
All of my S&W handguns cost 2 and 3 times more now than what I paid for them. They're a good investment and will last generations if taken care of.
