Mastodon has imo dogshit discoverability. For Lemmy it feels like posts across the federated instances are all elegantly aggregated onto my front page. I can also easily subscribe to subs on other instances.
On Mastodon the client has to work around the backend to do simple stuff like aggregate the posts of multiple instances. Most stuff in the federated feed is pretty much random and the local feed is restricted to your account’s instance.
User discoverability is also awful. If I dont have a user’s exact name and instance it’s nigh impossible to find them outside of my own instance. Searching lemmy is much more effective when it comes to external instances.
Mastodon is trying too hard to be a twitter clone in some ways I feel. If it had instance subscriptions a hit like how lemmy lets you subscribe to subs it would be way more useful. Right now it feels like everyone is shouting into the void.