They all have their purposes. One whack with the inertia hammer and normally the bullet moves enough to be re-seated. I use a collet puller for taking down a large number of loads (rarely, but it happens). Sometimes I bump bullets deeper with the seating die. I'm happy that I have all of them.
If I could only have one I'd go for the inertia hammer for cost and universality, but IMO it's a good thing I can't only have one.