I'm on Mastodon, Bluesky, and X. Most of my network seems to have abandoned X at this point. Bluesky has the most of my old network. Some of those are also on Mastodon.
In terms of UX and algorithm, X has a one size fits all algorithm that seems to favor a lot of crap that I really don't care about. If I switch to the Following feed, it's a lot more similar to other networks. That crap isn't coming from my network. It's very polarizing and it's the reason people are voting with their feet. As a product, it has stagnated. Whatever this product lead was doing, I don't think it's made a difference.
Mastodon's algorithm is basically sorting by time; I actually appreciate that but it has its limitations. It means my feed is utterly dominated by a handful of prolific tooters which is causing a rather low signal to noise ratio.
Bluesky has the most promise in terms of filtering and having lists. And it's federated nature means there are a growing number of third party things being built on top. And I like that it has multiple feeds that filter the content in different ways. It's actually very close to what Twitter was before they started locking down their APIs, shutting down third party applications, etc. It's essentially a better Twitter. And the at protocol is interesting relative to Mastodon. Its take on federation is more about interoperability and less about everybody trying to run their own private servers. You can. But you don't have to. Like Mastodon, there are also a growing number of use cases that go beyond being a Twitter clone.
Tangled is a very interesting at proto based application that is still a bit immature. It's the first take on challenging Github as a social network for developers that I've seen that might actually work.