I know that it is instinct for some folks to choose an external safety. I believe that the problem is that you will look at it prior to shooting. Your response is to say that you can carry your gun with the safety clicked off. Granted, but I still believe that you will look at it before you fire or - at a minimum- it will cause you to hesitate. That is why Glock's trigger safety is best. There is nothing to think about. When you are ready, place your finger on the trigger and pull. If you don't pull the trigger, a Glock will not fire. In a defensive scenario when your endorphins are screaming, You will appreciate not having the distraction of an external safety.
IMHO...