There are many benefits to a threadless system. In our shop, which mainly deals with mountain bikes, we keep on hand many different lengths and rises which then can be swapped to find just right stem for a customer. This takes very little time and effort on our part and you dont have to mess with the handlebar tape, grips or brake levers. The customer feels you have gone the extra mile to help them get the right fit. Also, they are much easier to repack the headset when that time comes around, just three 5mm allan bolts. Then when it comes time to put it all back together adjustment is so simple, not to mention the headset doesnt work loose, but generally that isnt a problem with road bikes. For my own personal bike when it is new I leave the steer tube a bit longer and use extra shims until I find the right height then cut it. With that said, give me a quill stem for my classic road bikes.
Mark with rain on the way