Choice Between IDOC and ABAP Proxy

Hello All,

We are building a Bi Directional Interface for Business partners between a third Party ERP, XI and SAP CRM.

We are looking for some advise on the best way to go forward between the two options below:

a) Do an ABAP Proxy Call on Fn Module CRMXIF_PARTNER_SAVE from XI

b) Create and IDOC in CRM

( Message Type CRMXIF_PARTNER_SAVE_M )

Not being an XI consultant, my understanding is as follows

Option A : Gives me the flexibility to format my response in the manner we like. But this is a synchronous call. Also this is a generated RFC. So changes in the XIF layer of CRM could be an issue.

Option B : Response can be achieved only through the ALE Audit Functionality, which has a predefined message structure. For Eg: If I wanted to send the response in the same format as the incoming message with an added segment for the error, this is not possible. Ofcourse, I get all the functionalities of monitoring and Handling IDOCs in this option.

Any thoughts on the advantages and disadvantages of each option would be greatly appreciated.

Thanks

Anoop