I'm on tildes, it's really refreshing and easy to use.
Main difference is that it seems to cater more of a serious adult conversations, which after years of being able to predict most comments before looking in Reddit, is very refreshing.
Lots less memes, communities are pre set and can't be created, seems to be to make sure to populate them before creating sub categories that people may see as in active and avoid.
Overall it feels like fedworld is best overall experience, squabbles is memes and lighthearted and tildes is more deep and thought out style of interaction.