JMOfartO:
Well, if reliability is your first priority, then you can find no better choice than a 3rd Gen Smith..
I've had, or still had, a 3913, 3913LS, 5906,6906, CS9, CS45. (Well, actually i still have them all with the exception of the CS9 because I sold only because I had several other compact 9's).
Here's my take on the 6906 vs 3913.
The 6906 is a double-stack, thereby "thicker" than the slim 3913 (or 3913LS). The downside is the thickness, the upside is a greater capacity.. In fact you can use the 15rd mags from the 5906 (w/SW mag adapter) and you get a 16rd capacity.. Nice for a self defense firearm. I actually prefer the feel of my 6906 WITH the 5906 mags, and the appearance is absolutely factory.
The 3913 is a single stack.. Easier to carry concealed in an iwb holster if that's you thing.
Both pistols, in my experience, have been absolutely reliable, and if you do your research you'll find reliability is a given in these fine pistols.
For me personally, I prefer the "looks" of the 3913LS over the 3913, but that's just me. Both are excellent pistols.
I believe the 3913 has ambi-decockers (safety's) while my LS on has it on the left side (for righty's).
In fact my "bump in the night" nightstand choice is my 5906 w/Crimson Trace Laser.. It's big, it's heavy, but recoil is almost non-existent and it's tack driver (using the laser), and a pleasure to shoot.
As to which of the two (3913, 6906) 3rd Gen Smiths to buy?
IF I were buying one or the other, knowing what I know from having the opportunity to shoot and carry both choices I'd recommend the 6906 over the 3913 (or even the 3913LS)
Here's why.
I have pretty much standard sized hands, and the 6906 just "fits" MY hands better than the excellent single stack 3913. The 6906 has roughly 50% greater capacity (using the adapter and the 5906 mags), and in a self defense firearm, MORE capacity is a good thing..
I'll try and attach photos of my 6906, one with the factory fingertip mag & ten round capacity, and the other with the mag adapter and the 15 rd. mag of the 5906. As I said before I actually prefer the "feel" of the 6906 with the larger mag, and as you can see in the photos using the larger mag actually "looks" normal.
It's my opinion that 3rd Gen Smiths are highly UNDERRATED, under appreciated, and very reasonably priced..
Getcha' one or two, you won't be disappointed..
Good Shootin'
Jesse