Turned out to be irrelevant. Following their instructions I couldn't get EC2 runtime hosts to attach after a couple hours of fucking around (which is my standard for, 'is this mature enough to use'), while with ECS I hit one button and was up an running. Wasn't a hard choice when we started dockerizing (especially since I could simplify most jobs even further having dev use Fargate, albeit at a premium).

EKS struck me as a feature parity product, not something you'd actually use.