CRM-MDM Integration via XI

Dear Gurus,

I have worked on various ECC-XI-MDM scenarios where in the communication is done using IDocs and XML files.

Now i am starting up a scenario on CRM-XI-MDM Integration. Wherever i read on SDN, i found out that for exchange of messages between CRM and XI, ABAP Proxies are to be used.

I want to know if IDoc XML conversion can be used here(if not, then why not) or proxies are the only way? Please guide me on the same if the scenario is to be done via proxies regarding creation of the proxy, its calling, execution etc.

Thanks in Advance,

Shweta.