Originally Posted by Oscar

Threadless is supposed to be lighter because the set-up does not require a quill to be fitted into the steerer. (I wonder how much weight that saves.) What you lose with threadless is the ability to adjust your stem. If you want to try to raise your handlebars with an aheadset, you have to buy another stem. With a quill stem, you just raise it. My vote (6 roadbikes worth) is for a quill stem.