They are both excellent, but when you place them side by side you can hear the difference. If you hear just one it would be hard to know what it is. To complicate things further, not all artist cassotto accordions have a mano reeds.... not even all the ones with convertor... and then there is still a difference between the regular artist cassotto and the "gold" or "silver" series. There I have not been able to hear a difference.
Another complicating factor is that Bugari has changed reed supplier a few times over the past decades... and even with a mano reeds the sound is different between different brands.
But... what I have experienced by listening to and playing (and tuning) many accordions is that most sound differences between accordions are due to the reed blocks, more so than due to the reeds on these blocks.