Who carries?

The downside of open carry is this, lets say your in a store with a concealed weapon and bad guy comes in looks around and then pulls a gun and starts shooting at people. You pull your gun and fire because you have already assesed that he looks suspicious and your senses and reflexes are ready so you have a slight advantage to reaction time. However lets say your in a store with an open carry on your hip and bad guy comes in looks at your gun and boom your down first. You never want to give your element of surprise. The bad guy asseses his situation and factors in threats and obstruction however if he cant see you as a threat then youve thrown a wrench in plan and now he doesnt know what to do.