With regards to the wing to express differences, aside from a few parts (trigger guard and group is metal not plastic, and I believe a few other parts are stamped vs cast), it's really just the finishing of the gun that makes it smoother. They take the time to polish and deburr it all and you'll notice the reciver wont have manufacturing marks or burrs on them. Since I am cerakoting my gun, this ment nothing to me, and like I mentioned, a judicious stoning and filing of the action elements made it as smooth as a wing without a shot being fired. I can literally use my index finger to cycle the action. The 'shoot 1000 rnds to smooth it out' club is right, but with my extensive background in manufacturing I know better than to let burrs bed themselves into other mating/sliding parts.
With just a few rackings from new the bolt assembly already started scoring the reciver and that's not good to me. But I'm an ocd kinda guy and my kit and the quality of the items I make reflect this.
For rail, I splurged on the s&j rail/high tube adaptor and this thing is BADASS. Their product is top notch. I'm looking into what I can/should TiAlN as I have access to that process (pvd) as well.
And as above said, why limit yourself to 2.75 when lets say there's an ammo shortage and 3" is all your local shop has....... Never limit yourself when it comes to a defence shotgun as flexibility is the whole reason in the first place!