If users mostly search with specific terms they expect to match exactly (product names, SKUs, exact phrases), full-text search is faster, cheaper, more debuggable, and doesn't introduce the "why did it return this irrelevant result" problem semantic search can produce.
When queries are conceptual rather than exact — someone describing what they want rather than naming it precisely, or needing to match meaning across different phrasing — that's the case vector search was built for, and full-text search genuinely can't do it.
Most real search features that matter end up combining both — full-text for exact-match confidence, vector for conceptual fallback — rather than picking one. Starting with "which one" is often the wrong framing from day one.