I will likely be picking up a new road bike frame and I have the choice of threaded vs. non threaded headset and fork. It comes with a 1" threaded now but the seller will swap that out with new forks if I want to. Any advantage in going non threaded?
Kev is correct. Most new road bikes (if not all) come threadless. Quills offer more flexibility in hight adjustment. I cannot see any major difference in maintenance, etc. I think the trend away from threaded is due to speckmanship, competition and customers being obsessed with weight. The threadless maybe little cheaper to make as well, it is less flexible/adjustable, but not impossible to do many things with various stems. I can still find parts for either variety. The current fad is threadless.