How much benefit would there be to using WSDualHttpBinding with IIS hosted service vs. a client poll that calls the WCF service, assuming in the latter the service cached the data in question?

This scenerio would be for a notify type of service where the clients need to be notified by the service when an event occurs.

Specifically, what advantages would WSDualHttpBinding provide over polling? ie: Less network traffic, faster to design, easier to maintain, more control ???

From what i understand, WSDualHttpBinding is less scalable than client polling, so why use it at all? Edit: As Matt supplied, time critical can be one reason for the duplex binding.

Here is what i have so far:

WSDualHttpBinding

adv: can get immediate response w/o waiting on polling timer

dis: less scalable than WsHttpBinding dis: less firewall friendly

I'll add to this based on comments, please let me know if i state anything incorrectly.

thanks for you input :-)