Just looking at them side by side, apart from the obvious larger bore, the polini has D shaped transfer ports and thre smaller boost ports open top to bottom, while the malossi has triangle shaped transfers like stock just larger and two larger boost ports with some cylinder wall for the rings to stop on at the bottom of the stroke.
Malossi also has sunken piston ring pins that the ring covers all the way, and earless wrist pin circlips, and seemingly some extra meat inside the port channels to ramp them and make them smaller keeping the mixture velocity up.