James here, one of the co-founders of Electric.
Both projects are doing active-active CRDT-based sync. Our focus is on sync via Postgres and on compatibility with existing Postgres-backed applications. So you can drop Electric onto an existing Postgres-backed system and it works with your existing data model.
There's also quite a lot of difference in the development model, how we handle migrations, shape-based partial replication, etc. And we're not focused on p2p sync -- for us, everything goes through Postgres.
Hope that helps -- you can read a bit more about the system design here: https://electric-sql.com/docs/reference/architecture