B2B Adapters and XI Adapters

What are all the Advantages and Disadvantages of having a B2B Adapters Vs the XI Adapters?

I am trying to understand what a B2B Adapter will do and still not getting the correct answer. As my management is in the process of buying a B2B Adapter and I need to support them with my comments why its needed or Why its not needed. Plesae help me.

Any useful documents please share with me mohinimrm@yahoo.com yes my email id is Mohinimrm@yahoo.com

Appreciated.