Sorry, I had to go back to work. Besides, Tom did a good job sorting out this stuff. As others have said, marketing plays a big role in all of it. The "compact" style road bike's main advantage is fewer sizes supposedly fit more people, instead of making a 49,50,51,53, etc., they just have a small, medium, large, and a not so extra large. If you're built like me, most makers don't provide a frame big enough.