I had to dig out my notes from college (good lord, I forgot how thick that binder is; I could write a doctoral thesis from that stack of paper). Pima cotton (often called Egyptian cotton) is Gossypium barbadense, while upland cotton is G. hirsutum. As of 2003 or 2004 (whenever I took that class), Pima cotton made up about 5% of world production, and 3% of US production. Upland cotton is the other 97% of US production. Lint yields of Pima cotton tend to be lower than upland cotton, but like Five Lock Boll said, the lint quality is generally superior.