Can't agree. I've had both on bikes, once on the same bike - at least a Cinelli 1A and a Nitto Technomic Deluxe. To adjust vertical on either one, you loosen the quill bolt, hit it with a wrench or something to knock the wedge or cone loose, and then you have a loose stem in a fork - total adjustability. If it doesn't work this way, there is some corrosion making it tough to break loose - i.e. the stem was not greased before installation.

One thing that does make a difference is a wedge offset quill clamp versus a cone expander quill clamp. The cone design takes up less space in the steer tube. If you have a small frame, the extra centimeter will make a big difference. Despite the taller quill, I can't identify a difference in stem stiffness, at least not in my recollections of riding the Masi with both setups. Nearly all Nittos are wedge, though I think they may have sold some Pearls with cones. Vintage 1A's had cones, as did vintage 3TTTs.

The Tech Deluxe and Pearl both have the hbar clamp bolt threading into a nicely shaped nut that is virtually impossible to strip, and is a lot more robust than the captive allen nut used in vintage Cinelli 1As - I once broke one from over tightening. Since then I went to using a torque wrench - finding specialized Italian replacement fasteners is a PITA. Better not to break anything in the first place.

So: stiffness and finish, even as far as I can tell, depending on model of Nitto. Quill clamp: Cinelli vintage takes the nod. Hbar clamp: Nitto if the top models (Tech Deluxe yes, Technomic no).

Michael, I'd say (as did someone else): choose your bars based on planned usage and your fit requirements, select a stem dimension to fit the bars on the bike and position your hands properly, then select a stem that meets your constraints (quill rise, extension, clamp size and aesthetics/style) - top-down, function-driven design. I wouldn't worry about if one flexes a bit more than the other.