So the class was fantastic! I learned a lot from the instructor--in fact I plan to practice a bit and then do some more personalized instruction soon, just to make sure I'm building some good habits from the start.
I got to try all sorts of pistols. I think the list included:
Glock 19
M&P 9c
M&P 9 shield (single-stack)
Springfield XD Mod.2 3" and 4" models
Springfield XDS 3.3" (single stack)
Ruger SR9 and SR9c
He suggested I do a separate class on hammer-fired pistols if I really want to see the differences, but we stayed with with just striker-fired for the class yesterday. I learned quite a bit. I found that (and granted, this is the voice of total inexperience talking) the different lengths of guns in the same family (like the Ruger and Springfield) made very little difference to me, and I don't think I really felt any more recoil or snap on the shorter barrels. Accuracy is a non-issue because I can't shoot straight yet anyway
If anything those more compact models just simply fit my hands better.
I found that I could shoot the compact guns pretty comfortably with or without the magazine extensions. Whether my pinky finger was resting on the grip or curled under it, I seemed to have a very good hold of the gun and good control. The optional "pinky extenders" pretty much solve the issue entirely for me.
The only ones in the bunch I disliked were the Rugers. I can't really say why--they just didn't do it for me. They seemed jumpier, and had all kinds of stuff going on--thumb safety buttons (tiny), big "Loaded When Up" bars on top, huge logos emblazoned on the slides. At any rate I had no desire to shoot them again.
The single stack guns weren't very easy for me to grip, although I'm sure practice would fix anything, and both were surprisingly soft to shoot and didn't flip around as much as I thought they would. The little Shield really impressed me.
So really, I'd rate it as an almost dead-even tie between Glock, S&W and Springfield, with the Springfield (especially the sub-compact) being the gun I most enjoyed and came back to overall. That and the S&W seemed to feel more natural to me than the Glock. I liked the S&W trigger the least. I like the simplicity of the Glock design the best.
I think I've learned that I like the smaller pistols a bit better, somewhere in that 3-3.5" range but double stack. I will spend some time comparing what may be a list of "finalists" now that I will guess includes:
Glock 26
M&P9c (maybe...that hinged trigger was a little weird)
XD Mod.2
I know there are others--sig, Walther--I could probably shoot for all eternity and not run out of options
Just based on yesterday, if someone said I had to buy a gun without further thought, I'd get the Springfield. It just worked. But I don't think I'd have any qualms about owning and relying upon any of the ones I tried (short of the Ruger which just didn't click with me).
Should be fun!