Comment by quambo

Both use local SQLite and keep the backend authoritative. The main difference is that PowerSync mostly handles downstream replication and gives you an upload queue; your API still owns the write semantics. Syncular specifies the whole round trip. Durable commits, auth scopes, conflicts, replay, revocation and bootstrap. Syncular also goes further up the stack: schemas plus SQL/SYQL generate typed queries for TS, Swift, Kotlin, Dart and Rust, and blobs, CRDT/encrypted columns and windowed sync are built into the protocol.

In my separate benchmark harness, Syncular currently does considerably better than the tested PowerSync setup. For example, 100k bootstrap is ~0.57s vs ~6.5s and offline replay ~35ms vs ~5.1s. Those are early results from one environment, though, not a universal claim (https://github.com/bkniffler/offline-sync-bench).

I've used PowerSync in the past with a huge initial bootstrap sync and was very frustrated by the performance back then (ca 1 year ago), which was one of the reasons to create my own library.

PowerSync is much more mature today obviously and still a great and proven tool.