A route table entry vs. a real ENI in your subnet.
Gateway endpoints are free; Interface endpoints ARE the PrivateLink mechanism.
Gateway endpointInterface endpoint
ServicesS3, DynamoDB only100+ services via PrivateLink
ImplementationPrefix-list routeENI per AZ, in your subnet
CostFree$0.01/hr/AZ + $0.01/GB
Both now support IPv6 — including dual-stack Interface endpoints provisioning both address families on the same ENI, closing a real, recent gap for IPv6-only workloads.