Two of the best Rugers I have were chambered for .38spc. You have to watch +P rounds as the Security-Six is such a fragile gun (JOKE!).
But seriously, here's the advantage of having a .38spc: you can have a good gunsmith ream out the chambers to take .357s. Many manufacturers do a fast and loose reaming of chambers, and this can easily affect the accuracy of the handgun. When you have a gunsmith ream out your chambers, he can easily ream them out accurately. Just tell him you want them chambered for jacketed hollow points. When you get the gun back, take six 125 JHP bullets and drop one into each chamber from the back. Each bullet should catch in the chamber. Don't push the bullets through as you'll resize them; however, watching the tolerances is one reason some guns are inherently better than others.
Both of my guns were Service-Sixes. After reaming them to accept .357s, these guns became some of the most accurate revolvers I ever owned. I've seen some very good guns that have let JHP bullets fall right through the chambers. I ordered a number of Colt Trooper Mark IIIs for people where about three of every six bullets just fell through. I bought a girlfriend a Taurus 66 that was just beautiful, but the chambers in that gun were, as far as I could tell, just holes. I couldn't hit the broad side of a barn with it.
Once you've had the gun reamed properly, ask the gunsmith about whether the Ruger would benefit from an 11º forcing cone. I can't remember whether it benefits lead bullet accuracy or jacketed bullet accuracy, but it's worth asking.
It may be tempting to ask for an action job, and if you have the $$$, you might want to have the gun smoothed out some. But the best way to do an action on a Security-Six is to repeatedly dry fire it. And replace the mainspring.
The Speed-/Service-/Security-Sixes are some of the best .357s ever made, in my view. And the truth is, Ruger was nuts for replacing them.
