All valid points, but if you want to consider wether it wins you the game or not, here's something that is usually in everyone's subconcious but nobody thinks of mentioning it:
Having a long barrel means you give away your position more often when hiding behind a barricade. Think about it. When you fire, a plume of smoke comes out of you barrel because of the compressed air. Longer barrel = more likely to see that smoke if you, say, shot at the tape from your barricade. Someone in your mirror will probably see that smoke if you have a longer barrel, ergo, you get mugged easier
Back players generally use longer barrels for the accuracy and range. Theyre easy to spot even if they try and hide because all they SHOULD be doing is shooting non-stop.
Shorter barrel = worse accuracy BUT easier to conceal yourself completely, even when shooting.