Something else that u might consider is support available for the product u select. Do they have 24 hour 366 day support? And how many free support areas are there on the Internet. I don't know anything about any other products, but Avaya has many sites such as this one with very helpful persons that give free advice. I am not pushing AVaya, although it would probably help me stock, just trying to 'hit all the bases', so u can make a good decision.