Inferno was positioned back then as some kind of a ressearch thing not suited for production.

Preact pros was:

- very small size (it's near 5kb Non-Gzipped without compatibility layer), perfect for lightweb mobile apps (Inferno was like 60kb, React 250kb)

- has less gimmicks for porting from React and an optional compatibility layer to enable some of low-level React libs and components

Preact has no synthetic event system wrapping, if you heavily relly on it then things could be rough.