Embeddings are what make semantic search possible. A query about "reducing customer churn" can surface a document about "improving retention" because their embeddings are near each other, despite sharing no vocabulary. This is also their limitation: proximity in meaning is not precision, which is why embedding search alone performs badly on exact codes and identifiers.
Two operational rules matter more than model choice. Embeddings from different models are not comparable, so changing the embedding model means re-embedding the entire corpus. And what you embed matters as much as how — chunking documents along their real structure, rather than every fixed number of tokens, is usually the difference between a retrieval system that works and one that returns fragments.