As far as I can tell, the Y seats are the same.
As for J:
The KL 789 seat is a cheaper version of AF’s seat. (Zodiac Cirrus, when done right, one of my favorite J seats.)
The 78X has the JAMCO seat, which I’m not familiar with.
Both have all aisle access, which I vastly prefer over any seat that involves me having a seat mate opponent (like KL’s A330 and 777).