If you play the role of a sniper you want the longer barrel, it will keep the accuracy up.
Another nice mod I liked when I had my 98- Strip the weapon down, with a dremal and a light wire brush go over the casting the bolt rides on to smoothen it out then polish. It will make the mechanical noise level go down. Swap trigger springs with a ball point pen for easier trigger pull.
There are a few forums out there with plenty of mods, I cant remember the names it been a while.