I have no center seat, so my decision was between driver and passenger side. I had also heard that driver's side was safer because of the instinct to protect yourself.
However, a friend of my sister had an accident in which her daughter was killed because she was behind the driver's seat. When the car was struck in the rear, the driver's seat collapsed and the weight of the driver (the mom) crushed the little girl (5 years old). Apparently, this is a defect in just about all cars and could be fixed inexpensively. Since rear impact collisions are not rated by crash tests, there is no incentive for carmakers to correct the problem.
pease, I am so glad you brought that up. I don't really have much info. to add but I was in a crash when I was little and the same thing happened to me that happened to your sister's friend. I was in the back seat behind my mom and my brother was in the front passenget seat. We were struck from behind and my mom's seat collapsed back on to me. My brother's seat did not collapse back. This was probably about 25 years ago. It is so sad that this same problem is still happening.