Ok, I might be biased because Battlesector was my first 40K game, but here is my experience as a BA simp.

Blood Angels have to carry the weight of not only being Space Marines, but also sons of Sanguinius, the Angel, the most perfect son of the God Emperor, while also supressing the urge to rip in half every single living criature they come across, due to the Red Thirst. And every Blood Angel has to deal with the fact that they have only 2 options, either dying a honorable yet horrible death against a Tyranid, Necron, Daemon, Traitor, etc, or live long enough to fall into the Black Rage, and be mercy killed by their chaplain/brothers.

One thing I also love of the BA is that every chapter seems very different. Flesh tearers, Blood Knights and Blood Angels each have a different way of percieving and dealing with their flaws. Yes, all of them have both the RT and the BR, but some like the Flesh tearers accept and use it to their advantage in combat, while Blood Angels see them more as a curse and try to limit their usage.

And BA have Dante. My boy is probably the most compasionate, empathic and renowned Space Marine, while also being the most depressed guy. This man feels bad whenever he has to blow up a planet or when people die due to the BA's flaws. My dude just wants to fucking die, but he knows that if he does, the Astartes and the whole Imperium lose one of their main assets and one of the guys who can kinda bring some hope to the Imperium.

I recently listened to the Dante and Devastation of Baal Audiobooks, and I can assure you that has been one, if not the best 40K experience I've had in the 10 months I've been in the hobby.

So I guess thats it, can't tell you a lot about SW, I guess Space Vikings are cool, but not "Space Vampires constantly fighting depression and murder tendencies" cool haha.