As far as your gun choice, it's highly personal. What caliber do you want to carry. Do you want a revolver or a pistol? Don't forget to add in extras like a holster, spare magazine/speed loader, dependable light (80% of all self defense shootings occur at night), and a good belt.
I've never heard about those issues with small of back carry so I'm glad you guys made me aware of them, just seemed like the most comfortable to me.
I've heard that revolvers are the most accurate so that appeals to me but at the same time I'd sacrifice a little bit of innacuracy for more rounds in a self defense situation. I understand that most situations occur within 5 feet so I don't think a pistol will sacrifice enough accuarcy to make a big difference in a situation like that.