I'm still playing through the series, I finished 0 and Kiwami, still waiting for my gpu so I can play K2 (it uses dragon engine so I need something that is mid-range by today's standards)
For the two games I've played so far, 0 is my fav, Kiwami feels a little worse boss wise and fighting wise, EXP system isn't really my thing, I preferred the Money for upgrades system over it