I converted from MySQL (before whole MariaDB and fork), and I've been happier with every new version. My biggest moment of joy was JSONB and it keeps getting better. Can we please make the connections lighter so that I don't have to use stuff like pgbouncer in the middle? I would love to see that in future versions.
FWIW Mysql 8 has gotten a lot better in standards compliance and ironing out legacy quirks, with some config tweaks. While my heart still belongs to PostgreSQL things like no query hints, dead tuple bloat (maybe zheap will help?), less robust replication (though getting better!), and costly connections dampens my enthusiasm.
The benchmark linked in the comments shows 7-38% improvements. Nothing to scoff at, but if you need PGBouncer that probably won't make enough of a difference.
It certainly isn't much of an improvement in connection latency (the connections are still pretty heavy), but it is a massive improvement in transaction throughput with higher numbers of connections. If you scroll down a bit, there is now higher TPS even at 5000 connections than previously could be had at 100 connections. That fixes a massive amount of pain that previously only could be solved with pgbouncer.
I'd be curious to see if the concurrency improvements in PostgreSQL 14 help with increasing the threshold for when you need to introduce a connection pooler.
Lighter connections would finally allow for using lambda functions that access a Postgres database without needing a dedicated pgbouncer server in the middle.
