OpenID Connect vs. SAML
Choosing between OpenID Connect and SAML is not just a matter of using a newer protocol (OIDC) instead of the older more mature protocol (SAML).
In most cases Keycloak recommends using OIDC.
SAML tends to be a bit more verbose than OIDC.
SAML has its uses though. As you see the OIDC specifications evolve you see they implement more and more features that SAML has had for years. What we often see is that people pick SAML over OIDC because of the perception that it is more mature and also because they already have existing applications that are secured with it.