[Drew]

For those that don't know what one or either of these are:

Both are a programs which allow a server to operate a "voice chatroom" of sorts for people to come together and talk while playing games, etc.

The differences...

Teamspeak2 is by far the more popular of the two programs, mainly due to its more friendly graphical interface and the abundance of TS2 servers out there. The audio quality could be compared to a CB radio.

Ventrilo is far less appealing in terms of interface, however the clarity of the audio is unmatched by Teamspeak. The audio for Ventrilo could be compared to a Sprint cell phone.