Streaming video is substantially worse than GTV, in every way but two: 1. You don't need the game files to watch streaming video, and 2. With streaming-video, you can do things like conduct video interviews.

Because the game files in Quake Live are free, problem #1 is irrelevant. So what if, to solve the second problem, you built into the Quake Live/GTV system a streaming video/audio player? That way, without the need for multiple programs, you have built-in commentary, and the ability to conduct video interviews (plus, you enjoy the low-cost, high-quality and flexibility of GTV). The negatives from each are eliminated, and the positives enhanced.