Ignoring the need for a Synchronous Replica, you may see Aurora Postgres extremely costly and not too great in performance compared to PostgreSQL. This has been neatly documented in this Article

https://www.migops.com/blog/is-aurora-postgresql-really-fast...

Well, this behaviour of Oracle may be debatable too.

INSERT INTO test_number VALUES(10.0500);

SQL> SELECT * FROM test_number;

         I

---------- 10.05

Anyways, I am more interested in how PostgreSQL can make us have trailing zeroes or no trailing zeroes depending on the type you choose or other work-arounds.

I think there is a way to get the inserted trailing zeroes in Oracle as well. So if you explicitly inserted 10.0500, you want to get 10.0500 but not 10.05 ?