The performance benefits of a real DB server with local NVME and a TB+ of ram can save TONS of engineering effort/time. I have ran 10TB+ PostgreSQL DBs in both

The performance benefits of a real DB server with local NVME and a TB+ of ram can save TONS of engineering effort/time. I have ran 10TB+ PostgreSQL DBs in both the cloud and bare metal and TBH, in terms of time required to maintain, there isn't a huge difference once you move beyond what RDS can do. That being said, if RDS can do what you need USE IT. You can always migrate later and it will save you the need to hire someone who really knows postgres.