I think that

State machines are more concerned with the actions that can take place. FBP is more concerned with the data that is moving through the system.

is a fair assessment of the differences. With a state machine, you want to make sure that you can move through the states of the machine to some valid exit state; if so, then the machine has succeeded, else you failed. With FBP, you push data in and wait for data out, but if nothing comes out, that's just a valid response as if you did get data.

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Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important