I regularly carry a second mag on me. Some on this forum will carry 2 or more spare mags. We all have to draw the line somewhere, and for me it is a fully loaded pistol (9+1) with a spare 9 rd magazine.
Obviously, carrying a 2nd magazine is favorable because you're carrying more ammo, but it has other benefits as well:
- it permits you to do a tactical reload during a down time in a drawn out conflict (replace & retain half empty mag with full mag)
- in the event of a significant malfunction you're able to drop the magazine, clear the chamber & load a fresh magazine.
When OC I usually carry the spare mag in a pouch on my weak side. When CC I usually just slide the mag into my pant pocket on my weak side.