Originally Posted by GhostRider62

For a variety of reasons, I sometimes use a 110mm stem on a particular bike but usually 150 mm. I notice the difference in handling.

Also, the closer the center of gravity is to the wheel axis, the more difficult it is to balance and steer a bike.

Sitting upright with Porter bars has your head in a normal position from a balance perspective (vestibular) and the higher position makes balance and steering easier

I suspect what I notice is a combination of the above factor and more. I really noticed these things when on an extremely far flung recumbent

Differences in frame geometry, materials, and layup are probably bigger factors in handling response than stem length. I have two bikes with about the same length. One of them is a handful on twisty, bumpy steep descents. I was on the other one going down a hill that always took my attention on the lousy bike (Cervelo). My first thought was, "This bike is slow downhill" and then I looked at the Garmin and the speed was the same (about 40 mph) but I could almost take a nap, that is how different. 140 vs 150 mm stem. Totally different geometry and material