optic 100%, have you ever used a red dot? it speeds up your game/reaction/aim massively. You dont have to look down it like with iron sights or a scope. rather it functions a lot as if you where using a laser, in the sense that you keep both eyes open, see everything as you'd normally see it except you have a dot where you're aiming at... and you can aim in the dark with ease.
I really dont see how the bipod would even compete. you can aim without it, use terrain the support your rifle or just use a simple pair of shooting sticks made from sticks n rope or tape.