Is there a sweet spot of asteroid size/energy required to adjust orbit/danger (etc, obviously I don't know all the parameters) Like, you don't want to waste ti

Is there a sweet spot of asteroid size/energy required to adjust orbit/danger (etc, obviously I don't know all the parameters) Like, you don't want to waste time going after a bunch of tiny asteroids, but if they're too big it would take too much delta-v to move them. Or I might be wrong entirely.