For example, it supports proper ALTER TABLE which doesn't force you to recreate tables and copy data around when you go beyond the most trivial use cases.
This is pretty much the only discussion I've found on this site:
What it gives you over both is single-file databases which are easy to share, and in-process embedded mode, just like SQLite.
Unlike SQLite, it doesn't only support embedded mode, but can also be turned into a "server" DBMS that supports remote access from multiple clients (like MySQL/PostgreSQL). Hundreds of concurrent connections work fine from what I've seen. This can be changed in either direction at your discretion, the database file remains the same.