For me, I knew I would be in an agency for the next 20 years that issued 9mm. Add in wanting to standardize on 9mm (J-frame, P938 and now, Glocks)… it was an easy decision. Only non-9mm gun I regularly carry is a LCP Max (.380). And that is because I cannot find a 9mm in that size.
But the performance factor was also a nice benefit. I still have a matched .38 cylinder, all of which done in NP3 Plus… which allowed for easy/fair comparison.