Postgres by far. The inbuilt json support is great. In addition, Postgres as a whole has decades of bullet proofing behind it. MongoDB doesn't have many advantages, has many bugs and sharp edges, and doesn't have enough advantages to justify it's use. In [an old analysis by Jepsen](https://jepsen.io/analyses/mongodb-4.2.6), MongoDB 4.2.6 exhibited "read skew, cyclic information flow, duplicate writes, and internal consistency violations. Weak defaults meant that transactions could lose writes and allow dirty reads."
Will note that json/text columns are better than jsonb. Lower serialization overheads and surprisingly smaller binary size. Or better yet, just normalize to a columnar format.