PostgreSQL is an SQL database that also offers full-text search (FTS), with extensions like pg_search it also supports BM25 scoring which is essential for lexical search. SeekStorm is centered around full-text search only, it doesn't offer SQL.

Performance-wise it would be indeed interesting to run a benchmark. The third-party open-source benchmark we are currently using (search_benchmark_game) does not yet support PostgreSQL. So yes, that comparison is still pending.