Yeah, games have been very SMG friendly in the past, and that's way more noticeable on PC than on consoles. As far as I know SMGs have less Aim-Assist than ARs, which kinda balances it. On the other hand strafing (and also spraying) are more effective on PC, which again makes SMGs more powerful.
One thing though, the 2 most powerful weapons in competitive play (imho) in BO2 are Assault Rifles: the AN-94 and the FAL. When it comes to getting kills in a public game, nothing works better than an SMG.