From what I’ve seen, there’s no real difference between lemmy.ml, lemm.ee, and lemmy.world. They’re all the same attempt at trying to be a Reddit clone with the same Reddit defaults as comms. If you merge all three instances together and merge the comms that they share, they would be absolutely zero difference. I guess lemmy.ml is lemm.ee with socialist characteristics while lemmy.world is lemm.ee with fascist characteristics. To me, the biggest difference between those instances is how they see us and whether they are federated with us.