Just sharing my personal experience with this:

I used Gemini multiple times and it worked great. I have some weird symptoms that I described to Gemini, and it came up with a few possibilities, most likely being “Superior Canal Dehiscence Syndrome”.

My doctor had never heard of it, and only through showing them the articles Gemini linked as sources, would my doctor even consider allowing a CT scan.

Turns out Gemini was right.

Ventrilo was awful, having huge delay. Also no persistent chat.

TeamSpeak is proprietary and required a license for more than 8 users iirc. Chat might have been persistent?

Mumble was/is king in terms of voice chat. Open source, fully featured, strong certificate based security, best latency. It’s used as backend in many big games, too. No persistent chat, though.

We used IRC for chat and Mumble for voice like 10 years ago when I played Eve Online. Works great!