Voyage AI is the "specialist's choice" for embedding models, now backed by MongoDB's engineering muscle. If you are building RAG for legal, finance, or heavy codebases, their domain-specific models (like voyage-law-2) are arguably the best in class. However, for generic chat apps, the premium pricing ($0.12/1M tokens for top-tier) might be overkill compared to OpenAI's commoditized options. The new `voyage-4` series (released Jan 2026) brings Matryoshka embeddings to the masses, allowing you to truncate vectors to save DB costs without losing much accuracy—a killer feature for large-scale deployments.