Dispatcher and SynchronizationContext classes in WPF

1. Use the Dispatcher when your code is tightly coupled to WPF. 
2. Use the AsyncOperationManager when you need to queue something on the 'Context' thread. This works with Windows Forms, ASP .NET and WCF applications as well. 
3. Avoid using the SynchronizationContext yourself. The AsyncOperationManager uses this mechanism internally. 

Note:

SynchronizationContext.Current object is of type DispatcherSynchronizationContext which is actually just a wrapper around the Dispatcher object and the Post and Send methods just delegate to Dispatcher.BeginInvoke and Dispatcher.Invoke.

So even if you decide to use SynchronizationContext I think you end up calling dispatcher behind the scenes.
Besides, supposedly, it is a bit cumbersome to use SynchronizationContext as you have to pass a reference to the current context to all threads that need to call into your UI.