Built into Opus:
[ul][li]Synchronize panel[/li]
[li](Copying Updated Files may also be of interest.)[/li][/ul]
The built-in Sync panel may be all you need. But, if not, you can use Opus to launch dedicated diff/merge tools which are even more powerful and integrate well using either of these scripts:
[ul][li]"Smart" front end for Beyond Compare[/li]
[li]External Compare and Merge Tools[/li][/ul]