What is smoother, a v6 engine or a water cooled, radial aircraft engine? I know it is nutty question.?

What can I say, I am curious.

I wonder if a radial 7 cylinder engine makes power with greater smoothness than a V-6 car engine. Yes I know, a V-12 aircraft engine is smoother than both.

Call up your grandpas from WWII if you can to answer this one. Those old guys know everything.