Maria supports partitioning, Postgres (as of my last knowledge) does not.
Unstructured data is more flexible in Maria natively, but Postgres can support it in a variety of ways.
You can find lists and lists of head to head comparisons out there which will highlight all of the niche differences that each brings over the other.
Ultimately either will work just fine for 99% of use cases.
PostgreSQL's manual indicates that partitioning is a thing[1]. Is the something different than what you're thinking of?
One of my projects has the need to drop millions of rows a month based on the time period, and I've been considering a switch to postgres because they also have a module that will do that automatically.
What am I missing?
[1] https://www.postgresql.org/docs/current/ddl-partitioning.htm...
Is it the kind of thing where the TimescaleDB extension would make sense?
Modern versions of postgres have all the partioning features you'd expect (except automatic ranged partion creation)