Welcome Holo, good to see another OC'er here. As for your choice of a handgun to purchase for open carry I would advise trying several guns out before making your choice A gun that fits your hand will be a lot more intuitively accurate for you. When a gun fits you it should feel like an extension of your hand, You have spent your entire life learning that when you want to point at something you point at it, no need to sight down along your index finger to make sure. It should be the same way when you have a gun in your hand you look at the target, the gun comes up, you squeeze the trigger and the bullet impacts where you are looking. A good way to check fit is to hold a gun (not in a death grip but firmly ) Pick a target, lock that target in your minds eye and then close your eyes and bring the gun on target when you think you are on target open your eyes. Don't worry if you are not pointing directly at the target what you are looking for is the angle that the barrel is resting at in relation to your sight-line If it is cocked up or down the gun may not be the best fit for you If you are looking parallel right down the sights then hold that one aside and look for guns with similar grip angles. On a side note the 1911's grip angle seems to fit a majority of people exceptionally well and itis mimicked in the Springfield XD as well as the Smith & Wesson M&P. Sams gun shop has quite a few of these guns available for rent and you should try several before making your final choice. As for caliber you will take into account not only what you are comfortable shooting but your wife as well, Bring her along when you are hunting for a gun though it is usually best to get two guns one for you and another one that is fitted for her as it would be very rare that you would both fit the same gun.
PS. I am no longer working at Sams but everyone else there should be able to help you with your purchase,
Good luck, 47