There is often confusion as to when to use Sync Frameworks or Replication.  Sync Frameworks can be used to synchronize data stores whether they are databases or even a file store whereas replication is about synchronizing SQL databases. 

These two synchronization mechanisms also target different audiences.  Sync Frameworks targets the developers and provides more flexibility.  It also imposes more coding as in the case of the non-database store, the developer must code the providers.   Replication targets the DBAs and furnishes out of box procedures and monitors.

The following table also provides insight into how each mechanism addresses key features:

Key feature

Merge replication

Sync Services

Synchronize by using an n-tier or service-oriented architecture

No

Yes

Supports heterogeneous databases

No

Yes

Incremental change tracking

Yes

Yes

Conflict detection and resolution

Yes

Yes

Easily create data views on the client

No

Yes

Automatically initialize schema and data

Yes

Yes

Supports large data sets

Yes

Yes

Query processor is locally available

Yes

Yes

Automatically propagate schema changes

Yes

No

Automatically repartition data

Yes

No

 

More info can be found at:

http://msdn.microsoft.com/en-us/library/cc281959.aspx

http://msdn.microsoft.com/en-us/sync/cc470041.aspx