It's not just the perfect natural balance of an inline-6 that makes it smoother than a V6 in terms of engine vibrations.

An inline-6 has a regularly-spaced firing order of the cylinders, i.e., once every 120degrees rotation of the crank. This has 2 effects:

- the torque delivery over the crankshaft is smoother (v-sixes need might need higher flywheel mass and/or harmonic dampers to smoothen this out)

- the exhaust pulses are smoother (nothing sounds like an inline-six at high rpm)