Headless can be faster at the top end – but a well-built traditional store is already fast, so for most stores it’s the more sensible choice.
A traditional WooCommerce store (WordPress theme rendering the storefront) can absolutely be fast when it’s properly optimised – sub-second loads are routine with good hosting, a lean theme, and tuned caching. Most stores that feel slow are simply un-optimised, not held back by the architecture.
Headless (a separate Next.js-style frontend) can push speed and interactivity further, and scales superbly – but it costs more to build and maintain. Its edge is real mainly for large, high-traffic, or highly interactive storefronts.
The honest guidance: don’t go headless to fix slowness that a good traditional build would solve more cheaply. Optimise the store you have first, and consider headless only if you’ve genuinely hit its ceiling – here’s when not to go headless. More: is headless worth it? · how to speed up WooCommerce