In my opinion (I'm in the right section, am I not?) carrying concealed only on occasion is ignoring that attacks can happen anywhere at any time. As we have seen lately, the less likely we think the venue is subject to attack, makes it just that much more a place for a successful surprise attack. Thinking that in large, well-attended public events there are likely to be "armed professionals" who will defend the unarmed, is a risky assumption. The professionals may not be exactly where they need to be when an attack occurs. The only person who is absolutely going to be present to defend you in the event of a violent attack is you. If you're armed you stand a better chance of surviving. The type of attack is, of course, a mitigating factor.
In the matter of open carry, unless you can do the Vulcan Mind Meld, you really don't know what the motivation is. However, I don't think open carry is smart. There are too many ways you can be relieved of your firearm.