9mm requires subsonic to take advantage of a suppressor. 147gr and up is usually subsonic. American Eagle Suppressor 9mm is 124 great though.
.22 you have bulk high velocity which is usually subsonic out of a 4.5-5" or less barrel. Then you have standard velocity like CCI standard that is subsonic and then you have subsonic like Remington, Gemtech, and AE Suppressor which to me is even quieter.
.22 is going to be cheaper and quieter to shoot then 9mm.
What can do you already have?
Can't find that American Eagle subsonic 124 gr bullett anywhere online? Are they still selling that?