Truthfully, I don't see much difference. a ferrull is only needed to keep the end of the shaft from mushrooming or cracking and it doesn't take a very long ferrull to prevent this from happening. I believe the lengths that are common is more tradition and looks than any real benifit.
Here is my opinion. I feel the harder the ferrule the better the cue will play with shorter ferrule. It will take less of the natural feel away from the cue. With softer ferrules the longer the ferrule the more cue ball action it produces. So the length of the ferrule does change the hit. The thickness of the wall of the ferrule also changes the hit.
Chris www.cuesmith.com www.internationalcuemakers.com