Played the MSX version this time. Despite actually having an opening cutscene and even an additional level, I think I altogether prefer the SMS version. The screen is larger/sprites are smaller on the MSX version, so enemies more easily build up in large numbers (something that the persistent sprite flickering and slowdown suggest is beyond the prudent limits of the system). Enemy patterns also feel more repetitive, particularly in the level missing from the SMS version (I think) and particularly with an enemy that spirals vaguely towards your ship, which takes far too many bullets to kill for the high numbers it spawns in with.