[Asterisk-Users] call center design question

[TC]

>Sure, here it it goes.
>When a call is about to be transferred to that extension, an * AGI sends
>the client all information that was programmed to be transferred. We had
>to patch app_queue.c to do this (giving it the ability to call an AGI
>just before a call is being answered by a queue member
Having gone down this route now, and the benefit of hindsight ...
what advantage do you find with made to * channel/app 
vs. listening on events from the manager interface
then doing your client communication when getting the correct state msg