Good question...I'm interested in what others have to say too.
I have done some research on the short barrel ammo...by reading other reviews online. Most folks that have commented on it, seem to really like it.
Now, I have not used their standard ammo, but I have used their short barrel ammo in my Glock 26 (9 mm). Its accuracy seemed to be off at first...I quickly realized it was me not having proper trigger control. After settling down, and focusing more, the short barrel ammo was just as accurate as any other at the distances that I tested...up to 15 yards.
I can't say for sure that there is any noticeable difference with the short barrel ammo in a short barrel gun. Hopefully, others we chime in with more knowledge then I have and enlighten us both.