I like kbin microblog twitter thingy feature. It was faster with less downtime at the time. It had more setting and I love customizing thing like round corner, color themes, sidebar on left or right, autoload post images, etc. I just have a better first impression.
I heard someone said kbin was newer with better scalibility compare to lemmy.world.
In the end it doesn't matter which one you choose. They both can view the same contents being posted. I like to think of it as choosing yahoo mail vs hotmail. Both let you send emails and both have different looks and feature.
Note I am like you and have no idea when it come to the technical stuff about this whole "federate" talk.