Hi,
When the replication happens between CRM and ERP, it is a normal and standard process to utilise the CRM Middleware for the replication set up. Because the scope of this middleware is huge and have more features when you utilise the same. Whenever you have the external systems, Legacy systems or non SAP systems you can make use of the LSMW to fetch data into CRM system.
If your primary aim is to synchronize the data between CRM and ERP, best is to use the CRM middleware and make use of its functionality. But if the replication is only from one end i.e. from any of the external systems, then you can be surely using the information present in my blog referred by Aditi. I hope this helps.
Regards,
Venkat