Because their stuff [Pepsi's] just doesn't taste as good. Although I am a Dr Pepper fan.

You seem to be implying that Dr. Pepper is a Pepsi product. It is not. Although Dr. Pepper is distributed by Pepsi distributors in some areas of the country, it is owned by Seagrams, which purchased the Dr. Pepper/Seven-Up company a few years back, which had previously been a totally separate company, and had been two separate companies before that.

In other areas of the country, Dr. Pepper is distributed by Coca-Cola distributors, and in those areas, it's often hard to come by its competitor, Mr. Pibb, which is a Coca-Cola product, as the Coca-Cola corporation often doesn't distribute its own product there, especially at soda fountains.