Platform choice is usually presented as a technical decision. In practice it is an operational one: who edits the store, how often, and how unusual the buying journey is.
Start with the merchandising rhythm
If campaign pages change weekly, editor ergonomics matter more than rendering benchmarks. A storefront the team cannot update becomes a storefront nobody updates.
If the catalogue is small and the journey unusual, a custom build can be simpler than bending a platform around it.
Headless is a trade, not an upgrade
Headless buys rendering control and costs you preview fidelity and some native features. Take it when a measurable constraint demands it.
Write down the constraint first. If you cannot name it, the classic theme route is usually the faster path to revenue.