Velocity..which means little in close range stopping power, but means a bit more if you plan to shoot at much distance.
Ask yourself what you're gaining in return. I don't want a mile long barrel that I can't turn a corner with, but honestly, I don't understand the attraction to short barrelled rifles.
I figure most of us don't do a lot of close quarters combat, and for most uses a standard length barrel handles well enough. Outdoors it gives an advantage, and indoors it isn't really at much if any disadvantage.
I guess that's why I've always wished the bullpup concept was more popular. Full size barrel in a compact rifle. I have the cheesy Muzzlelite bullpup stock on a Marlin Camp 9 and it's turned out to be one of my all time favorites simply because of it's natural pointability and handiness without having to sacrifice barrel length to get it.
As always, your mileage may vary.
