When to use OnMessageAync()?

Hello,

I'd like some advice about when it would be appropriate to use OnMessageAsync() instead of OnMessage() with QueueClient and SubscriptionClient. Since OnMessage() can receive messages on multiple threads, what value does OnMessageAsync() have?

Also, can anyone point to an example of using OnMessageAsync()? There's no example in the MSDN documentation nor in any Azure samples I've found.

Thanks!