Dies stay cleaner, fingers don't get greasy, ammo does not get greasy, guns stay cleaner, and I have noticed that in 30/30, 308, 22 hornet, and other rifles that group sizes tend to get smaller.
BTW, Brake KleenŽ is a great way to lean sizing lube out of your seating die. Just remember to seal the surface with a light layer of oil and blow out the excess oil