You are overthinking it. Yes, .357 is very good, but that doesn't mean it's the most practical for every situation and an N frame is a large, heavy firearm to carry. Not saying it can't be, but I don't want to every day.
So, off the bat I'll suggest a 9mm for a revolver simply due to ammo cost and availability. Both .38 and .357 are tough to acquire currenlty and the prices are still way too high for basic practice ammo, defense ammo is running well over a buck a round. With 9mm, I'd have to brush up and see what hollow points are doing good from a snub, I figure HST's would be fine, they always seem to work.
Why 9mm? It's got much more power than .38 +P, but it's not as nasty as .357 is in recoil. Given it's more manageable and the ammo is cheap and everywhere, you are going to practice with it much more than you would the .38 or .357 and that means you're going to become a proficient, accurate shot.
Now, if money isn't a concern there's the Chiappa Rhino, which fires the round from the bottom of the cylinder, not the top like a traditional revolver. That translates to less felt recoil and muzzle flip. If $1000 and 6 rounds of capacity is up your ally, then .357 is an option, but the reality of ammo availability and price is still omnipresent.
The challenge with a revolver 9mm is finding the right one for you because they're not as common. Ruger makes the LCR and SP101, the SP101 is heavier and will soak up more recoil. You obviously want an N frame for more rounds, that's fine, so there's also the Taurus 692 which is a 7 shot and comes with both a .357 Mag and 9mm cylinder. They're hard to come by now and the unported models aren't currently available and I'd never recommend a ported snub barrel for self defense.
S&W does make a 9mm revolver, but at the price they cost you may as well get the Chiappa Rhino.
Overpenetration isn't a major concern if you do your homework, but the reality is all hollow points are mechanical and they can fail under the right conditions. If you want to totally eliminate the possibility for overpenetration then ammo like Lehigh Defense Xtreme whatever the fukk solid copper ouchie bleedy bullet or the Inceptor copper polymer lightweight tumblepalooza don't rely on expansion to cause damage, they rely on magical bullet rotation and flutes that churn soft tissue into jelly to release energy. Also, due to the lightweight projectile the Inceptor ammo has less recoil. Throw that ammo in a Chiappa Rhino and it'll be like shooting a .22
Those are some of my preferred bullets for a short barrel snub revolver, especially those of a heavy, low pressure flavor like .45. They'll work fine in 9mm or .38 or .357 too.
357mag doesn't start to sail away from 9mm till you get to 3-4" in barrel on out.....
