Lemmy.world is the most chill instance so far and the mod announced a change of server, now it feels smoother now, but still there are some down times as more people comes by. Lemmy.ml is ways more moderated and needs sign up to access it, the comments from other instances doesn't show up or needs to be approved, some have like 10 seconds approval, and also have a smaller server with less ram than lemmy.world, so overall there has been problems and connectivity issues due to the influx of users coming here.
Lemmy.ml requires sign up i think for most of communities and also they heavily moderate (and poorly at that, constant bans and suspensions) wouldn’t recommend the main instance at all