One way is that it's really obvious what you're supposed to do with Tesseral! Like, here's our Go SDK docs:

https://tesseral.com/docs/sdks/serverside-sdks/tesseral-sdk-...

It's pretty clear what you're supposed to do. Keycloak can't give you that kind of clarity, because they're designed to accommodate products that are B2C/B2B, single- or multi-tenant. Sometimes Keycloak is an IDP or an OAuth gateway, sometimes Keycloak is a customer identity management product.

Keycloak requires you to have familiarity with technologies at a level beyond what most developers have worked with. When your customer says "I need to enable SAML, and require it for all logins", with Keycloak you now need to know how SAML works, how to configure it, and how to walk your customer through that process. (FWIW, they can't support SCIM at all, you need to install a 3rd-party plugin.)

In Tesseral, all you need is this [0]:

    import { useOrganizationSettingsUrl } from "@tesseral/tesseral-react";

    const Example = () => {
      const organizationSettingsUrl = useOrganizationSettingsUrl();

      return <a href={organizationSettingsUrl}>Organization Settings</a>;
    }

[0]: https://tesseral.com/docs/sdks/clientside-sdks/tesseral-sdk-...

I don't really understand the main difference advantage, except that you offer better support for business.