While there are a lot of differences Firefly and Expanse are both set only a few hundred years in the future. The solar system has been partly populated by humanity but interstellar space travel is still far from being a reality. In the expanse we have three major political factions: The Earth, governed by the UN. The Mars, once a science colony of Earth the Mars is fighting for independence and potential supremacy over earth. The Asteroid Belt, bands of workers who have been send to asteroid mines to harvest resources, they are quite suspicious towards Earth and Mars.
To all of you who just want to see some Balls/Pussies of Steel travel the universe and do some bad ass stuff. Don't worry you have a good cast of independent main characters who are caught in the crossfire and you know... blow stuff up.
If you are a sucker for Political Drama like me then the Expanse is a must watch though! There is really no good vs evil going on here. The Earth wants to keep stability, but also their position at the top and the people from Earth tend to be very phony and dishonest. Mars is technological advanced compared to Earth and while you would sympathize with them and their fight for the right to terraform the Mars, they are quite the warmongers and with their soldiers training in 1G their ambition to one day claim Earth seems to be obvious. The Asteroid Belt might be the most sympathetic at first glance, a bunch of poor down to earth guys who appreciate the little they got and mostly the people around them. However in the latter parts of the series this love for the community turns to a suspicion and even violence towards everyone who is not a Belter.
You can catch the series on Netflix (if you are a German citzen, not sure for US). It has good production value, great writing and awesome characters. It's funny that even though I am really not on board with a lot of the modern(!) feminist bs, I am still a sucker for strong women. Frankie Adams portrayal of Bobbie was maybe a little wooden at first, but I really fell for her in the 2nd part of Season 2. However she still can't hold a candle to Drummer - a female Russian officer in uniform with a tendency for violence. Who wouldn't love that?!
Bobbie
Drummer <3
If you want to talk spoilers in the comments just use the nsfw tag. That Finale at Venus! Jesus, what the hell is happening there!?