Lemmy is much better for developer/admins. There is currently 10+ Lemmy apps in the works and 2 apps that supports both Lemmy and K.bin this is because K.bin doesn't have a proper API documentation yet. Lemmy also has a better documentation for running your own instance and uses way less resources. Most of the Lemmy's advantages are technical ones but it translates to user facing ones with more apps, more responsive, has more users and can scale better