MicrosoftApart from connectivity - no matter which option you choose, there is one major deal-breaker in Teams (there are other minor things as well that might give you headaches):
Teams is not capable of recognizing "AzureAD Contacts" (or - as mainly referenced to "Exchange Contacts" - where Microsoft has a different understanding of that term than the vast majority of us) in searches. (Microsoft constantly refers to "Exchange Contacts" as a contact you save in a (user-) mailbox, which then the contact only is available for that single user...)
Meaning, you have a contact object in AD/AAD and you have a phone number listed in that contact, this contact is not found by Teams, which prevents centrally managing your (telephony) contacts org wide, while you can for email.
This functionality was there in Lync/SfB and until this is not back, there is NO feature parity between Teams and Lync/SfB.
