was going to do a diatribe against glocks. I don’t like them, but if you are comfortable with one go for it.
as far as caliber...depends how much weight and bulk you can carry. When I was young, I use to tote a Ruger Redhawk .44 mag on my belt all day while hunting...did not even know it was there....
now when I conceal carry, I feel weighed down by my tiny (but steel)Colt Mustang .380. My son bought himself a Ruger lightweight LCP the same caliber and it is practically weightless. now they have a similar piece in 9mm...the LC9...more power...I have fired both, and if you like DAO guns, these are hard to beat.
good luck with whatever you do...and watch out for the Gun Grabbers! it is open season on The Constitution!
Lock and Load
MOLON LABE!
I kind of lean towards the single stack for comfortable carry, although I miss the 40 caliber power and carrying capacity.