I have several stems. Older ones are closed face aluminum ones. One is a light weight cromo steel one I harvested last year from the LBS clearance table. It's lighter than the old aluminum ones, but seems to flex more. Latest aquisition is an open faced aluminum one. It's the kind with two bolts and lets you swap out the stem without removing the bar tape and brake levers. Haven't used that one yet. Oh, and my old MTB had an imoveable steel stem that weighed a ton.

Can someone enlighten me on the intended purpose of these stems and the relative trade-offs. My limitted experience indicates these categories:

Heavy aluminum or steel stems are cheap.

Thin walled chromo stems are light, but flex.

Lighter aluminum stems are stiff, but expensive.

I'm just inviting general comment on stem materials and their relative merits. Who would want a light stem? Who would want a heavy but stiff one?