40K Space Marine players are familiar with different options that each chapter can take. Every chapter can take almost all of the options, but the Blood Angels have been different since 2nd edition. They have special variants, and they don't want to share with the other children.
For example, in the fluff the Space Wolves were assaulting a planet and their Land Raiders were destroyed in some kind of accident. Lacking mobile lascannon support, they cannibalized their Long Fang lascannons and mounted them on Predator tanks, making the Predator Annhilator pattern. This worked well, and the design was almost immediately disseminated to all the other Space Marines in the galaxy.
The Blood Angels, on the other hand, have Furioso Dreadnoughts, Baal predators, overcharged engines (which now make their Rhino Chassis vehicles Fast) and most recently the Stormraven Gunship. Admittedly the Grey Knights also have the Stormraven, but that seems like an odd combo. No one else has these unique vehicles. I envision conversations like this happening when Sanguinius chapters meet other chapters.
Dante: Bro, what's up?
Marneus: DUDE! Just hanging out, how you been?
Dante: Oh, I gotta tell you about this sweet new tank my techmarines made. It's the Shizzle fo' rizzle!
Marneus: HELLZ YEAH!
Dante: So get this: We mounted a twin linked assault cannon on the Predator Turret. We call it the Baal Predator. Bitchin' huh?
Marneus: Aww, you gots ta get me that design, bro.
Dante: ...uh. Hmm. Well about that...
Marneus: Come on dogg!
Dante: Sorry bro, but no-can-do. Mephiston would kill me, and that dude is, like, totally psycho. Plus he's 250 points.
Marneus: Harsh, bud. Look, I got some girls coming over, you'd better go.
Dante: Oh. I see how it is. Later. Bro.