Use API-first when the target schema is stable
If your required fields map cleanly to an existing endpoint and freshness needs are predictable, API-first is the fastest path. It reduces maintenance load and lets you ship integrations earlier.
Use custom extraction when business logic depends on page context
Marketplace edge cases, variant-level pricing, and seller behavior often sit outside clean endpoint contracts. If those details drive your pricing decisions, custom collection plus normalization wins despite higher setup cost.
The expensive failure mode is accidental dual maintenance
Teams start API-first, then bolt custom patches without redesigning the pipeline. That creates two competing truth sources. Pick one canonical path per use case and isolate fallbacks explicitly.