Deploying Ejabberd for my Application - Doubts

Hi all,

I am looking for a solution for the problem that am currently looking to solve... I am trying to build a scalable XMPP Messaging system, where multiple bots(in the range of 1 for each country in the world) push out messages to clients spread all over the world. The main thing to be noted is that the clients have a roster size of 0, i.e. they will not communicate with anyone other than the bot assigned to it.

There can be anywhere between 10-50 Million Concurrent Clients, Messages are in the size of 2-3KB(Well formed XML), that can be transmitted in the both the directions i.e. Client->Server(bots) and vice versa.... My estimates put at the messages to be going outwards in either directions somewhere in the range of 50-100 messages/second.

The Clients will need to send/receive all the information as encrypted data using SSL+TLS and any other scheme..

Will the Tigase Server be a good choice for the kind of the problem I'm trying to solve..

Any help will be appreciated.. Also how much better is ejabberd in comparison with Tigase and Openfire?