Haha. This is te most discussed subject in Holland.
It seems very logic that a polish't surface is the best.
Butt probably it isn't.
Take the plane thing. Throu that it's as smooth as possible to reduce friction.
But with a moped engine there is more than just air!
There is also gas and oil. When you sand (not polishing) the transfer-ports. The oil that is in the mixture wil stick to the transfer-ports wall. This tiny oil surface is much smoother than that you can ever polish it. So? probably sanding the transfers is better than polishing.