Not once on my deployments have I ever thought "Man, if only I had an extra inch and a half of barrel..."
I say save length where you can. I see more benefit in having a little less material swinging around in front of you when moving/shooting than in... what, an extra 80fps according to mtnrider?
Size doesn't matter, it's how you use it!
Just doing what I can to stay on this side of the dirt.