If you are carrying a handgun for defensive purposes, you need to be able to get to it when you need it.
On the market today, there is a wide variety of holsters to choose from that vary in price from a few bucks to a few hundred; some are worth it, many are not. What most people forget when considering carry techniques for a handgun or any weapons for that matter is that they are going to have to be able to access the weapon in all environments with both strong and weak hands.