U-turn by itself is better than sub seeding, which takes two moveslpts.
Like dude said, Leech Seed has a ridiculous amount of hard counters. Why bother wasting time and health by dropping a sub and then being forced to switch when you could have just u-turned? If they stay in and let themselves get chipped to death, they are bad players. If you're waiting for its plethora of hard counters to be removed before you unleash the lukewarm wrath of seedicott unto your opponent, you are then sweeping with leech seed. Pick any other sweeper because its going to be infinitely more effective.
Like dude said, Leech Seed has a ridiculous amount of hard counters. Why bother wasting time and health by dropping a sub and then being forced to switch when you could have just u-turned? If they stay in and let themselves get chipped to death, they are bad players. If you're waiting for its plethora of hard counters to be removed before you unleash the lukewarm wrath of seedicott unto your opponent, you are then sweeping with leech seed. Pick any other sweeper because its going to be infinitely more effective.