We've taken a modular approach which is different from most. This enables you to only pick the features you want for your use case and not worry about unnecessarily complexity.
We provide far more flexibility and options on the frontend as well
KeyCloak is a small part of the Redhat (and even less significant for IBM, the owner of Redhat). For us, our team and company is 100% dedicated to building auth. Its do or die for us. While this may not sound tangible, we'll constantly be innovating (and hopefully out executing keycloak).
Keycloak does not offer a hosted version of the offering. In our opinion, a hosted open source product is still quite distinct from a proprietary SaaS product.
We provide the most robust solution for managing session tokens. We mitigate against all types of attacks and detect token theft using rotating refresh tokens. One of our libraries to solve for edge cases (browser tabs lock) is actually used by Auth0 as well and has 250K weekly downloads on npm.
Finally - in general, we've had feedback from Keycloak users that they've had a poor experience deploying and managing Keycloak and would switch to a good alternative, if there was one. I understand that this was not true for you.
If you do get the opportunity and decide to try out supertokens, we'd love to hear about how your experience compares between the two.