I would guess that the majority of legal concealed carry permit holders, when they carry, use the strong side position. It's kind of become the sanctioned or "approved" way. However, I think it is not the most effective. Even worn at 3:00 o'clock for a right handed shooter, the pistol will not be as easy to get to when one is sitting, or, especially driving buckled into your car seat. Moving the gun further back to 4:00 or 4:30, or worse, small of the back, just makes it worse.
Cross draw, especially for a right handed shooter, is the optimal carry position. You can get to your weapon quickly from almost any position. The seat belt doesn't interfere in a car. It is easy to get your gun hand on or in close to your gun without drawing attention to that fact. The same goes for appendix carry (1:00 o'clock for the right handed) but a little more complicated if sitting in a seat with a back, but not as bad as a strong-side position.
Cross draw has gotten a bad rap over the years, even though you'll see many photos of the old lawmen and Texas Rangers wearing their pistols cross draw. Must have been a reason. These days, if you were open carrying, like most law enforcement officers do, this would certainly put your gun in an easily accessible position when standing face to face with a bad guy. However, for us, wearing concealed, the bad guy likely won't know you have a gun in the first place.
It's a good position to use if, for example, a bad guy is close to you and you suddenly have to fend him off with your non-shooting hand. You can quickly fend, or block with your left, stepping back with your right leg, which is a natural movement in a fight, quickly drawing as your body turns and as soon as your gun becomes level it's pointing directly at him.
There are other reasons for considering cross draw. I had pretty much bought into the often stated notion that cross draw was old-fashioned, unsafe and not as effective as strong side carry, until I read a long piece on it in Gun Week by R. K. Campbell. You can find it here: http://www.gunweek.com/2005/feature0101.html
Given his experience and his reasoning, I had to re-evaluate my opposition to cross draw even though I was initally attracted to it. I suggest you read Mr. Campbell's article and decide for yourself.