The fact that you can:

(1) Find a server with a simple URL (no pw needed, no port or IP, etc.)

(2) Find your friends easily with a unique username and use chat as a fallback

(3) Create an audio room (that scales!) that has great audio quality (doesn't "drop" calls and

(4) Client that auto-updates to provide more and more features

All within a few minutes is a HUGE upgrade or Ventrilo.

This doesn't even mention the network effects, bot integration, gif/photo capability, etc. It's superior in almost every way possible.