Depends upon what I'm wearing which depends on the weather which affects what I'm doing ...
Some times Officer's model 45acp, sometimes Bersa 380, sometimes 22 revolver, sometimes S&W 629 with 6" barrel.
I bought and carry the Kahr 40 because of its size it was recommended to me by a cop in ohio its his back up gun. I also carry a LCP 380 as a boot gun as a back up. Both guns are very easy to shoot and conceal. I highly recommend both as a CCW.
I carry a Glock 21 and nobody notices it. Kahr makes a .45 ACP version of your pistol. Glock has their G26 .40, G29 10mm, G36 .45 ACP and G39 .45 GAP (which is a shortened .45 ACP casing, same bullet, but unable to fire in a regular .45 ACP nor can .45 ACP be fired in GAP pistol). Springfield has their line of of XD pistols and does H&K with their M&P line of Pistols.
I think a good addition to this question would be the percentage of the day you wear your weapon. I have my Sig P238 on my hip from the time I get out of bed till the time I go to bed and my days are 16-18 hours long on average. I of course take it off to shower.
I carry anything from a .32 Tomcat to a 9 mm. dependent on appropriate clothing for the season, how far into the cold cruel world (LOL!) I'm journeying and perceived probabilities of potential use during the sojourn.
Besides, don't want any of the armory "members" to begin to feel neglected! LOL!
Logic would tell me that you carry the biggest calibre that you can easily conceal, feel comfortable with carrying, and can actually shoot with accuracy. Personally, I know that regardless of those on the forum who find everyday life to be a small step away from murder and mayhem and must CC literally 24/7 with some form of bazooka, I am uncomfortable with anything on me other than my clothes, a credit card, a $20, and a car key; when I decided to minimally carry (in car for road rage, at night) it had to be small and very light or I would not bother. KelTec P3AT (380) does the trick. ,