So Functions could be treated as an opinionated, lightweight microservice framework, and thus you could compare it to other microservice frameworks like Service Fabric. Service Fabric is great for so many reasons. It can handle large, heavy duty applications. Functions is great for the opposite reasons, small & lightweight. You should be writing Functions like you'd write a unix tool; it should to one thing and do it well.

Cory is in the middle of a great talk where he helps "demystify" these services. (Which I can't find a link to right now...)