In my years working the street I experienced multiple occasions of suspects attempting to take my, or another officer's firearm. I can assure you that it is an absolutely religious experience to be in a fight to retain your gun. I taught weapon retention techniques and primal violence is the best way I can describe it as you know what he is going to do with it if he gets it.
As one of my instructors said in an academy more than 50 years ago, "There is always at least one gun present on every call or stop", The Level III retention holster is a great invention to counter gun grabs but still not 100%. In my opinion open carrying with an unsecure holster is simply irresponsible.
One attribute that Boxing and Martial Arts training usually provides is teaching you to keep your elbows close to your body which is one of the basics I teach in firearm retention and martial arts training.
I prefer to have my concealed handgun(and knife) to be close to my body, making retention a little easier.
When you're wearing a uniform and duty belt and the firearm is on your hip, it's harder to practice firearm retention. Fortunately there are good holsters for law enforcement that provide good retention(Safariland is what I used).
A uniformed officer and armed security officer has to deal with firearm retention issues that I concealed carrying civilian shouldn't have to(but that open carry creates).
You usually expect a uniformed security or law enforcement officer to be armed. When you see a civilian open carrying it gets your attention. That's the part some people don't get. Most times drawing attention to yourself as a civilian is not a good thing.
If you live in an area where Open Carry is common then you probably won't draw much attention.
If I open carried at any HEB store down in the Rio Grande Valley I can guarantee you I'd get noticed and most of the attention would be negative because it's not common down here. However, if you're at a ranch or farm in the Rio Grande Valley Open Carry wouldn't be a big deal because of rattlesnakes, coyotes, illegal aliens coming across your land, etc, etc.
Like others have said, know your laws, know your environment.