The Cortex + system runs similar Savage Worlds, lots of different dice ranging from 4 (worst) to 12 (uber). The way it comes in different is instead of hindrances you get distinctions to make you Big Damn Heroes of all sorts of variety. Plot points work like bennies and you can get them by taking a disadvantage in order to make the plot more realistic/human.
With Firefly its all about being relatable, find a job, get it done, move on.
The Cortex Plus System is a toolkit RPG system that evolved from Margaret Weis Productions, Ltd's Cortex System.