With snubs (I used to carry a 642 and now carry a Colt Agent pretty regularly), and this was extremely important for me, the decision for ammo is made exclusively by point-of-aim, point-of-impact.
You would have to test this.
I’ve had plenty of snubs where the only ammo that would shoot to POA was 148 gr wadcutters (advertised in the 650-700 fps range). Some would shoot everything unacceptably low except 158 gr LRN/LSWC (advertised in the 750-800 fps range). My Colt, for example, only hits POA/POI with 130 gr standard pressure FMJ (the USAF load). Heavier bullets shoot high, and it doesn’t stabilize them particularly well.
It all comes down to the height of the front sight, the dwell time the bullet spends in the barrel, and—this can be frustrating with snubs—even the shape of your grip panels and how well you grasp them. That’s right: changing your grips to something heavier and more ergonomic can change the weight and recoil characteristics of your snub, meaning your POA/POI can change with the same load.
Find the grips you prefer to carry and shoot, buy a couple of different bullet weights, and shoot deliberate groups at 10 or 15 yards. Something will shoot dead-on or close to it. Carry that. And buy a bunch of it for practice, because snubs are very demanding guns. They are capable guns, but heavy triggers and short sight radii leave little room for sloppiness.
At best, a .38 snub is going to throw a 9mm-ish bullet well below typical 9mm performance velocities—it’s a heavy-but-very-anemic .380 until you go up to +P and +P+ loads, and those suck to shoot and practice with long-term. A basic bullet going a reasonable velocity that hits the tip of the front sight is, in my opinion, the best a snub should be expected to do.