Neither - I use the force.
No, but really, both have the same effect in terms of the orientation your ship should end up in - seems to me the only real difference is whether your eye is focused on the center of the screen vs the enemy ship is. Maybe I'm just old-fashioned, but I'd have thought leading might be slightly better for this reason; your eyes would be focused more on where you're going.
Actually, there would probably be one other difference which might be important... If you were sitting idle and an enemy flew past your screen from left to right, leading should show you where to aim just before the enemy ship itself comes into view while trailing wouldn't give you a position to aim at until the enemy was on-screen. I'm not sure how much I've actually noticed this during play, but it seems like it could be an advantage to leading... maybe?