When each model fits
A large agency like MetaLab fits when the project is clearly scoped and well-funded, you need many specialists working in parallel, a brand-name partner matters (for the board or the raise), and the product direction is relatively settled. Their strengths are real: deep multidisciplinary teams, a proven process for large builds, and a portfolio that de-risks the choice for stakeholders.
A senior-led fractional partner fits when you're pre-seed to Series A, the product is still evolving, you want senior people doing the actual work with direct access, your budget is startup-sized, and you value speed and flexibility over team scale.