I am nearing the completion of my SC-900 draft content and can begin recording this weekend. The most interesting take away for me was  discovering in depth more about Azure AD B2C

I came Azure AD BC2 it in both the AZ-900 and AZ-104 but I did not know in detail what it did, but it appears to be similar to Amazon Cognito in that its a decentralized authentication service however Azure called it a "Customer Identity Access Management (CIAM)"

Azure AD B2C supports IpDs liked LinkedIn, Twitter and Github which are the most frequently asked by people wanting to use Amazon Cognito.

Azure AD B2C appears to managed mulit-tenant SaaS much better that Amazon Cognito. I haven't yet done a proper price analysis but it appeared quite affordable.

Its odd that I never hear anyone mention Azure AD BC2, its always about Amazon Cognito vs Okta vs Auth0