I'll blog more about this soon but here's a brief placeholder...
Service Fabric is Microsoft’s orchestration platform powering many Tier-1 Microsoft services such as Azure SQL Database, Azure Document DB, Cortana, Windows Intune, and Skype for Business.
Service fabric is an E2E PaaS platform, integrating many critical capabilities (e.g. container orchestration, service discovery, etc.) that allows you to develop, deploy and operate your applications (containerized or not). Service Fabric is a Windows environment with Linux and container support being added. Service Fabric is an ideal solution for Windows customers who may have some Linux workloads.
Azure Container Service is focused on deploying, scaling and managing Linux containers first, with Windows Server Containers being added. Customers using Linux container technologies should consider Azure Container Service. ACS is an ideal solution for Linux customers who may have some Windows workloads.