um xfire and ventrilo are two completly different things....
xfire is an messaging servce for chatting between users whilst they are in game and works across any game (it functions similarly to many IM services like msn or aim)
Ventrilo is VoIP software and allows users to logon to a vent server to chat to eachother.
The two are in noway comparable and do TWO COMPLETLY DIFFERNT THINGS.
Here at eGO many use xfire for keeping in touch when we are outside DoD or even whilst playing different games. For voice communication we use Teamspeak (this along with ventrilo are the main programs used for voice comms by gammers) but our server is password protected and only available to clan members