Some time ago I had the opportunity to chronograph (Oehler M 35P at 10 ft) a 9mm Wather PPS (3.2" barrel) with some regular Gold Dot +P 124gr 9mm (part # 23617). Five shots averaged 1179 fps, which is about 96% of the published velocity on the Speer website.

I'm just some guy on the internet so take this with a grain of salt, but I would not worry about velocity loss from a 3" 9mm barrel with premium self-defense ammo.

It is better to select a proven duty round from Doc's list and test your protection handgun for reliability with it. It is futile to worry about velocity, expansion or penetration if your pocket pistol jams when it is needed most.