The answer is not that one channel is better — the right choice depends entirely on your stage and objective.
When search ads are the right choice
Established search demand exists, you want immediate enquiries, and keywords are clearly identifiable. Search ads are ideal for reaching high-intent users actively considering a purchase right now.
When SNS ads are the right choice
You are building awareness in a new category, your product is visually compelling, or you want to reach a specific demographic. SNS ads are strong for reaching latent-demand audiences who haven't searched yet.
GRIP's recommended approach for startups
Before PMF: SNS ads for hypothesis testing — iterate rapidly on creatives and targeting. After PMF: scale with search ads. This two-stage approach is what GRIP recommends.