Umm ...

I think "shorter stem = twitchy steering" is a premature conclusion. While it is very true, you have to observe what you are doing while you are turning your handlebar. It "feels" premature anyway.

When I am using a short stem, I felt like I am "TURNING" the handle bar.

When I am using a long stem, I felt like I am "PUSHING" one side and "PULLING" the other. This isn't clear, but you know what I mean; with a 90-110mm, you aren't really twisting at the bar.

I think when I am riding long distances, it is mentally easy to maintain straight course with longer stem. I think this is because unlike with cars your weight is on the handlebar and it is easy to "SENSE" how hard you are PRESSING at the bar. With a short stem, you have to be constantly aware of "ANGLE" of the turning and this, I believe, is considerably harder. I am no sprinter, so I can't say about that.

I think unless sizing is a significant problem for you, it isn't a good idea to opt for short stems over longer one. (I repeat, this doesn't apply if sizing is a significant problem.)

T