The 239 slide release seems to be in an impractical place to me by what I am seeing. Anybody have experience with the 239 controls?
Interesting question to which I'll pop in for a second.
When it comes to the little SIG compact, I've found that some shooters who favor high/neutral thumb holds can sometimes unintentionally either engage the slide stop lever prematurely (locking the gun open with ammo remaining in the mag), or else they "ride" in inward/downward, and that pressure prevents the slide stop lever from locking back on an empty mag.
Neither of these occurrences are exactly convenient, but it's one thing to run dry and have to reload, and it's another thing to
still have ammo that can be fired, but the gun can't fire without you having to address some totally preventable shooter-induced problem.
The second of these shooter-induced problems is annoying, meaning many folks think that have to do a tap-rack-assess, only to discover they really only have an empty mag. That takes time and can be distracting (probably not something for which they "train", or practice).
The first problem may be worse, because now you're no longer able to shoot, but you have ammo in the mag that you could be shooting, if not for a thumb problem.
I had an instructor bring me a P239 .40 that he said belonged to another cop, and that the gun needed to be fixed because it was frequently locking open with ammo still in the mag. Might be a weakened or damaged mag spring, right? Unless ...
When I asked about the gun's owner, I was told he was familiar with SIG's, having carried an issued full-size SIG .357 at another agency, but he carried the compact P239 .40 off-duty at present. When I asked, I was told he was also right-handed.
The instructor who brought me the gun was familiar with SIG's, but didn't carry one, and was also right-handed.
We went downrange and I couldn't get the gun (shooting right-handed) to exhibit the "problem", but the other instructor managed to replicate it a couple times (shooting right-handed). I asked him to shoot it left-handed, and he couldn't get the "problem" to reoccur. (No slide stop lever on the other side, so that's a hint, right?

)
Now, the larger double stack SIG the P239 owner had carried and used for a long time usually sits in the hand a little differently, meaning it's easily possible for the smaller 239 to fit in his hand differently and position his thumb just at the wrong spot to bump the slide stop lever upward during the little .40's recoil.
The solution? Move the thumb, of course. The gun was working normally, as designed, but it seemed the shooter probably required a little "adjustment" in order for the gun to run normally.
I just relate this to illustrate how some folks might have a grip (and thumb position) that's fine with some pistols, but which might sometimes contribute to the potential for causing an issue with another pistol.
The 3913 has a forward slide stop lever. It's a reach for some folks who use the slide stop lever to release the slide.
The 239 has the slide stop lever far back at the rear, right under the ball of the thumb for many shooters, the grip is a little wide (changing thumb position for some folks). Just make sure an errant thumb position
and thumb movement under recoil doesn't interfere with the proper function of the control levers at an inopportune moment.
Now, if you're left-handed, and the gun you're using doesn't have an ambi/right-side slide stop lever, it's one of those little blessings.