Depends a lot on bike geometry too. Some bikes have much taller head tubes than others resulting in the need for different stem angles and spacer to put the bars in the right spot. My Specialized Sequoia has the stem adjusted to about a -10 degree angle whereas my LOOK has a 10 degree stem pointing up. The bars on the LOOK are still lower and I'm more stretched out on that bike because of the longer top tube. With the stem flipped, my drops would be useless as I'd have no room to move my legs (I guess that's why the "Pro" drops are more shallow).