Short answer
Choose an architect when design independence, custom exploration, and separate bidding matter. Choose design-build when speed, budget feedback, and one accountable delivery team matter more.
Independent architect path
The architect helps define the project before a builder prices it. This can produce better design control and more bidding leverage, but it takes discipline to keep drawings aligned with budget.
Design-build path
A design-build firm compresses design and construction into one team. That can reduce handoff pain, but homeowners need clarity on pricing checkpoints and ownership of plans.
The wrong move
Do not ask three design-build firms, two architects, and a drafter to solve the same vague brief. That is not diligence; that is project chaos wearing a nice jacket.