People who ascribe to the "element of surprise" theory, in my opinion, have watched way too many movies.
What are you going to do? Whip your gun out from under your clothing during an attack and yell, "Surprise motherf***er!!"
One could make the argument that those that wish to have the element of surprise are also those that have fantasies about being a hero or having a chance to use their firearm in conflict resolution. After all, it's not about prevention any more - it's about surprise.
I carry concealed when it is prudent to do so. I carry open when I can. My motivation with both methods of carry is singular: to be afforded an opportunity to neutralize a threat should I ever find myself in that position. I do not seek attention, nor do I wish to "surprise" someone.
As for the "cause alarm" argument: that is also a weak stance, built around conjecture. A properly holstered, openly carried firearm is no cause for alarm. And while it may offend some people to their core to see or be in the presence of a firearm, it is not a panic-inducing activity - unless you're one of those rare people that would fit the clinical definition of hoplophobe. But last I checked, we don't force police, security, and military to cover up to placate those few. While it may be shocking or surprising to see a non-uniformed person carrying a holstered firearm, it's hardly "alarming".
These petty arguments that divide our "community" drive me insane. Carry what you want, however you want. I'll do the same.