aah
Go for the .38 Super if you still can. Drop in 9mm Luger barrels may be available depending on the ramp size (width) for a reasonable price, from several sources Bar-Sto, Ed Brown, Wilson, and others, plus Kimber if there is enough interest. Even if drop in barrels are not available, .38 Super is a great caliber and well worth having. .38 Super was the first semi-auto caliber to approximate .357 magnum performance, so it will be a lot of fun.
If the barrels are available then you will be in the situation of being able to switch calibers easily like revolver shooters can do from 357 magnum to 38 Special, with just a barrel change.
Str8_Shot