Kswiss,
Good question.
According to Speer - the "short barrel" ammo has powder blended for a different pressure curve, intended for subcompact guns, and the projectile has been tweaked to expand the same as the regular Gold Dot at lower velocity.
http://www.speer-ammo.com/ballistics/ammo.aspx
You are suppose to obtain the same results whether you are using your G26 or your G17.
I have never done my own tests to confirm this but that's as much as I know. Perhaps someone else can fill in the blanks here.