Setup and time to launch
Shopify is a hosted SaaS: sign up, pick a theme, connect a domain and payments, and you can sell the same week. WooCommerce is a WordPress plugin — you first need hosting, WordPress, a theme, WooCommerce, payment plugins and often a caching/CDN layer. A serious WooCommerce build usually takes 3–6 weeks; a serious Shopify build 2–4 weeks.