Wow...loaded question..
First, in my experience the Security 6 is similar in size to the m19. My brother had a 4" Sec-6 and it was a very accurate revolver. Trigger wasn't terrible by any stretch, but I found it not as silky smooth as my 19-3. IMHO, it's a very good quality 357 on a budget compared to the price of the average P&R m19. And I do like Rugers cylinder release almost as much as Smiths. They actually designed it to be easy to use with a push down on the lock rather than awkwardly pulling back with the thumb like Colts which I find cumbersome..just me and my taste.. nothing whatsoever against the Ponies....
I have a 4" m19-3 and I absolutely love this revolver for easy to carry horsepower. I know it has been said over and over again, but the balance of a 4" K-frame is as close to handgun heaven as it gets. Everything about my 19 is everything it should be. Silky smooth DA pull, amazingly light yet crisp single action. I wish my Remington 700 deer rifle had a trigger like my m19!
586 is going to be larger framed and heavier. The L-frame Smith is as rugged as it is pleasing to the eye. Just decide if you like blue (586) or stainless (686).. or both!

My first Smith was a 6" 686. An absolute pleasure to shoot and handles stout magnum loads with ease and comfort compared to lighter framed 357's. Downside is they are a bit heavier if comfort during long term carry is something you require. Also obviously a bit less concealable due to their larger size.
Now the 28... My new favorite Smith 357. I no longer have my 686.. Still plan to procure another L-frame down the line.. But I replaced it with a 6" m28-2 Highway Patrolman. The m28 being the flat, non polished finish is a more utilitarian than it's much prettier sister the m27. This N-frame is about as rugged as it gets for 357 with few exceptions. The sheer size of the N-frame platform gives you super thick chamber walls and a forcing cone that I'm sure can take many thousands of rounds of full house mags with a smile. The first time I fondled my 28-2 at the LGS I was intrigued, the first time I fired it I was in love. Stoutly loaded mags feel like 38spl out of almost any other 357 revolver. But like the L-frame 586 and 686, the N-frame is big... It will be a bit heavier than the L-frames and naturally that much more to conceal.
Basically, this is just one man's opinion and worth what you paid for it. But what you have touched on is that there is a 357 mag out there for just about every possible need or desire. It's all up to you to figure out what you want.