Looks like Strapi has paid only features. Are these significant to most sites?
https://strapi.io/pricing-self-hosted "Free...Up to 3 default roles"
https://strapi.io/blog/introducing-strapi-enterprise-edition...
Sanity.io doesn't seem to be fully open source: https://github.com/sanity-io/sanity/issues/978
"You can only run the Studio connected to the Sanity hosted backend. There is no option for connecting the Studio to another backend."