Short answer for decision makers
If you need speed, senior expertise and a complete system, start with an agency or SEO OS partner. If you already have traffic, product complexity and enough budget to hire specialists, build an internal SEO team. If you need control and execution quality, use a hybrid model.
For AI search visibility, the hybrid model is often strongest because it combines internal knowledge with external expertise in GEO, AEO, entity SEO, technical architecture and prompt-based measurement.