Mastodon vs BlueSky - differences

Hey, I wanted to ask someone who has probably more knowledge than me about it - what's the difference about these two services? I know Mastodon has ActivityPub, so it works with Lemmy, and BlueSky has it's own kind of federation, but does it even has anything to federate to?

I'm asking not which one is better, I'm searching logical argument for one or other. I'm obviously more leaning toward Mastodon since I'm here, but I wanted to give my friend, who is thinking about joining, some real arguments.