Socom 16 vs Scout Squad?
16.25" or 18"?
The 18" Bush, Scout, MK14 Mod 0 & 1 are the better option.
You get a little more muzzle velocity from the 18" than the 16.25", but the biggest difference is how easy it is to change front sights and muzzle devices on the 18" compared to how difficult it is to do the same on a 16.25". The 18" uses a castle nut just like the 22", the 16.25" uses a proprietary one piece gas lock front sight base and muzzle break.
Shorties: I have owned 3 different M14s with 18" barrels in the past, and I currently own a single M14 with a 16.25". My CQB-16 type SEI is an awesome rifle that I will keep, but I prefer an 18" barrel for the reasons stated above.