Not in expert in either but ATProto services (what they call AppViews) are substantially different from the fediverse because they rely on a shared relay instead of explicit federation.
I'm conflicted about the costs of what is currently effectively global discovery, but it's not just another Mastodon.
E: I think its funny multiple other people said the same thing in the time it took me to write this
Note a relay is a perf optimization and doesn’t have to be a single shared chokepoint.
These days running a relay is fairly cheap (~$30/mo?), there’s maybe a dozen of them, and some apps don’t use one at all (instead relying on services like https://constellation.microcosm.blue/ for querying backlinks).
I'm conflicted about the costs of what is currently effectively global discovery, but it's not just another Mastodon.
E: I think its funny multiple other people said the same thing in the time it took me to write this