[zaarn]

(Last I checked atleast) JSON isn't as well supported on MySQl or MSSQL compared to PG.

In PG, a JSON column is so well integrated that you can do all sorts of crazy stuff (indices over JSON queries is my favorite). You could build an entire RDBMS on top of PG's JSON column.

[atwebb]

MSSQL indexes and provides dot notation/object query from 2016 forward, schemas are supported as well.