Caliber (and bullet choice for that matter) are primarily an academic exercise for anyone who is not a LEO / MIL and those guys are mostly issued a weapon and ammo and have no say in the matter anyhow.
A 115 grain 9mm FMJ in the right spot will stop the threat. I like heavier bullets because they carry the most momentum to punch through things that might need punching through. To that end, I have a habit of selecting rounds that are more on the heavier side for each caliber I own... thus the 180 in the .40 cal.
Personal choice... YMMV
17.4 (6), 19.3 (2), 19.4, 20.4, 21.4 (2), 26.4, 27.4
The 10mm has so much stopping power, it can even put an end to the caliber war.