A well-engineered access control system is really an identity system with doors attached. The credential and identity model matters more than the choice of reader technology.
Before specifying a single door controller, the design needs to answer: how is a person provisioned into the system, how is their access level determined and reviewed, and how — critically — are they de-provisioned when they leave. Systems that are strong on the first two and weak on the third are extremely common, and are where most access control risk actually lives.
Controller architecture should be sized for resilience, not just door count: what happens to access decisions if the connection to the head-end server is lost, and how long can doors continue to make correct decisions offline. High-security areas typically need local decision-making at the controller, not just at the server.
Integration with HR or identity systems is what keeps the access model accurate over time. A manually maintained access list drifts from reality within months; an integration that automatically revokes access on termination closes the single most common access control gap.