Disclaimer: k3s creator

Kind is intended to be a development tool to run fully upstream clusters using kubeadm in Docker containers.

k3s is a custom distro that is oriented towards lightweight environments. The scope of k3s and kind are different (distro vs tool to run k8s in docker). There is another project called k3d (https://github.com/rancher/k3d) that more directly compares to kind. k3d will run k3s clusters in Docker. k3d creates clusters significantly faster and uses less mem/cpu resources than kind.