Edge Delivery Services (EDS) and classic AEM Sites are not competing products so much as two different answers to the question "where should rendering happen?" Choosing between them is an architecture decision with real cost and timeline implications.
Rendering model
Classic AEM Sites renders HTML through Sightly/HTL templates on the publish tier, backed by Dispatcher caching. EDS instead pushes pre-rendered, highly cacheable documents to a CDN edge, with authoring happening in Word/Excel or the Universal Editor and content synced via a document-based pipeline. The practical effect is that EDS sites tend to hit near-perfect Core Web Vitals scores by default, because there is very little server-side work left on the critical path.
Authoring experience
Classic AEM gives content authors granular component-level control inside the familiar AEM author UI. EDS shifts authoring toward simpler, more constrained block-based documents, which is faster for marketers producing landing pages but less suited to highly componentized, design-system-heavy sites with strict layout rules.
Infrastructure footprint
Classic AEM requires a full author/publish/dispatcher topology, whether on-prem or as a Cloud Service. EDS drastically reduces the always-on compute footprint for the delivery tier, since most requests never touch AEM at request time — this is usually the strongest argument for EDS on cost grounds alone.
When classic AEM Sites still wins
- Deeply personalized experiences driven by real-time context or complex Target integrations
- Highly componentized design systems with strict authoring guardrails
- Existing large investments in custom components that are not economical to rebuild as blocks
When EDS wins
- Marketing-led landing pages and campaign sites where speed and iteration matter more than complex logic
- New builds without heavy legacy component investment
- Organizations prioritizing Core Web Vitals and infrastructure cost over deep authoring flexibility
In practice, most enterprises with a large existing AEM footprint end up running both in parallel — classic AEM for the core application experience, EDS for high-velocity marketing pages — rather than treating it as an all-or-nothing migration.