The choice between the various flavors of Azure AD mostly comes down to which types of external identities you want to allow, and what kind of app you are building. The official documentation has good comparison information between Azure AD B2B and B2C as well as a note on multi-tenant applications, but to help decide we've also published guidance in the form of an external identities decision tree.
DEMO - External Identities Decision Tree
- Walk through the content and main decision criteria on the Azure AD External Identities Decision Tree page.