I can see the benefits in both types of carry... open carry, everyone knows there are armed people there. The disadvantage is that it could/would make you the first target in the event of a shooter.
Concealed? Bad guys are not sure if there are armed people there, or not. Do I risk it? In the event of a psycho intent on shooting everyone, that is sort of a moot point, but in a store, or restaurant, it could work as a deterrent.
Concealed also helps in the sense that people with a fear of any kind of weapon won't be upset.
There are people at my work that get wide-eyed when I open my pocket knife.... "what do you need that WEAPON for?".....
I usually reply, "it's not a weapon, it's a tool, and I need it for what you see me doing right now, cutting open this box"....