Most Lemmy instances and kbin are connected/federated to each other meaning that the content is available to both. For example, the thread you currently are replying to is on the Lemmy.ml instance. So in general you don't need to worry if the content is on a Lemmy instance or on kbin. You will see it anyway. So you can just pick the instance you like the UI best and use that.
There is a small caveat, in that a magazine/community will only start federating/being visible on a remote instance after someone visits that community for the first time. E.g if someone creates a new community on kbin, then it is only visible on kbin until someone goes to newcommunity@kbin.social on their instance. And also other way around. If someone makes a new community on Lemmy.world you won't see it on kbin until you it someone else goes to newcommunity@lemmy.world on kbin.
Most Lemmy instances and kbin are connected/federated to each other meaning that the content is available to both. For example, the thread you currently are replying to is on the Lemmy.ml instance. So in general you don't need to worry if the content is on a Lemmy instance or on kbin. You will see it anyway. So you can just pick the instance you like the UI best and use that.
There is a small caveat, in that a magazine/community will only start federating/being visible on a remote instance after someone visits that community for the first time. E.g if someone creates a new community on kbin, then it is only visible on kbin until someone goes to newcommunity@kbin.social on their instance. And also other way around. If someone makes a new community on Lemmy.world you won't see it on kbin until you it someone else goes to newcommunity@lemmy.world on kbin.