The article contrasts Single Page Applications (SPAs) and Multi-Page Sites (MPS): SPAs load once and update via JavaScript for faster, smoother UX but add complexity and SEO challenges; MPS render each page server-side, are simpler and SEO-friendly but slower between pages. It outlines an e-commerce MPS-to-SPA migration workflow and highlights emerging hybrid CSR/SSR approaches, concluding that the best choice depends on project needs.