Data Replication in Oracle
A fast refresh would copy incremental changes over the network but requires that a materialized view log be created on the master site on the source table.  That adds some overhead to the inserts happening on the master table but would generally make the refresh more efficient.

A complete refresh would copy every row over the network every time the materialized view is refreshed.  That is likely to be less efficient from a refresh perspective but there will be no overhead to inserts on the source table and the master site does not need to create a materialized view log.

Oracle provides a host of data replication technologies-- materialized views are the oldest and probably the least efficient but are relatively trivial to set up.  Streams is a newer technology that has much lower overhead but is quite a bit more complex to set up.  Golden Gate is the preferred replication technology today but that has extra licensing costs.