Dear Mr.Sanjay Bangroo, Your explanation of the different technologies was very good. Could be better if we get to see the table.
However, I wonder what was your basis to declare that Avvaya, Alkatel and Nortel are the best PBXs around. Apart from other considerations, the Indian scenario has also got to be looked at. These players are not even directly present in India. Further, if you look at the quality of the product, Siemens is equally good if not better than Avvaya. I strongly feel you need to take a look at what Siemens offers.
I would however like to hear from you irrespective of your opinions in the above issues.