Why did Apple choose AT&T for the original iPhone?

I know this is an old question, but its been on my mind recently. I've read an article that claimed Apple first approached Verizon to be the carrier of the original iPhone, but were turned away. Later on, I discovered an article that was reciting a quote from the Verizon CEO that stated Verizon was never asked by Apple, instead Apple wanted AT&T all along. What is the actual reason for Apple choosing AT&T?

Another question that has been sitting on my mind; does Apple has a preference for AT&T over other carriers? Past events have led me to suspect that Apple prefers AT&T. The most notable have been Apple picking AT&T for the original iPhone, then choosing them again to be the first carrier of the iPad. AT&T also sells more iPhone's than any other carriers in the U.S.. These events have caused me to believe Apple's business relationship is stronger with AT&T than Verizon.