Neither. He's their "friend" which means he's a glorified pet. People will defend this till the cows come home but the truth of the matter is they don't treat him like family until that relationship is threatened. Spike should relinquish that control and learn what it means to actually be a dragon. It might be scary and cruel, but that's the reality he's going to eventually have to deal with. In Season 1 we've seen what happens to dragons when they get too big. They can't live around ponies anymore. I think the showrunners realized this implication in future episodes and retconned it so most of the dragons in the world are small.

Does this means dragons can't live together while they are small? No absolutely not. But contrast Spike to Smolder. She's friends with different species. She's not subservient to them.

Regardless of that, Spike is never treated as an equal but as an accessory. The one he claims to love with won't even let him let go of that delusion until he finally snaps out of it and she freaks out because of it.