Yes, you can see a comparison on Gitea's website. The Gitea community has put substantial development into growing Gitea into becoming a GitHub/GitLab alternative. I hope Forgejo will take it further, or that Gitea will actual work to become a community project like they promised.

The people starting forgejo were working on and with gitea before. With that I suppose the question is "Why fork anything but gitea?"

This is my question as well. If the majority migrate then I will follow.

Some of them have migrated. I imagine others are taking more of a "wait-and-see" approach.

For what it's worth, Codeberg is quite a major contributor to Gitea as well as the biggest public instance, and they are supporting the fork and will be switching over after the first stable release.