Let's go to the gun range, side-by-side. Let's see who can draw their gun and get two shots on target first. The person who open carries and simply has to pull their gun out of the holster and shoot; the person who at most has to lift up an untucked shirt
Actually, it depends on the person, and the amount of practice they've put in.
It may be a generational thing, but when I was coming up, good concealment was considered a must. As such, we practiced drawing from our setup, whatever it might have been. If I was any slower than someone of equivalent training drawing from an open-carry setup, the difference was likely too small to measure.
I have had people cite draw speed as a major reason for open carry, but I have ended up having to coach many of those people out of serious bad habits, including inefficient and/or unsafe draw stroke. I'm not saying all of them are like that, but a prevailing attitude has developed that, for some, equates open carry with an automatic improvement in survival odds.
I've spoken to too many folks who assume that a fast draw will save them. These are the same folks who don't know the difference between cover and concealment. There are many, many other variables to a gunfight than draw speed.
My attitude towards concealment has changed with the times. Even when concealed-carry reform was taking root, one could expect to get hassled by the police, regardless of the law. Officers on the street didn't (and can't possibly) know every wrinkle of the law, and they'd been conditioned by decades of training to treat a guy on the street with a gun suspiciously at best.
At that point, it was worth it to make the gun as invisible as possible. It was a big priority, and there was a lot of training around it. Generally, gratuitous printing was considered a sign of a lack of training.
Fortunately, things have changed in many areas. The police are better educated, and the populace is a bit more accepting. While I still carry "indifferently concealed," to quote Standing Wolf, I've found a good balance between comfort and a method of carry that's invisible to the average person.