From my experiences with both, mumble is a cleaner easier program to use. Teamspeak is not only visually unnatractive to me, but has so many buttons all over the place that I dont understand whats going on. Mumble is just so much easier.
I'll be honest, I don't think I'd ever install either Teamspeak or Mumble again, I can't stand either of them. I know a lot of people don't use it, or haven't heard of it, but Raidcall is by such an unreal amount the best out of any VOIP system. It takes the less computer resources and bandwidth, has the best quality with (in my experience) the best delay (or lack there of), and the best part is you can create a new room completely free that supports up to 10,000 users at any given time. Yes, 10,000 people for completely free all on dedicated hosting. It's great for game servers and guilds as well, the more people that use it, the higher the rank gets. The higher that rank gets it starts to show up on popular rooms, it's free advertising. Two of my favorite things about it; First how easy it is to get people to join, your room has a number, you give that number to someone, that someone puts that number in the box and hits enter, that simple. No IPs, ports or anything else complicated just a simple number. The other thing is users can stream music directly to channels within the group (that are allowed) which can make for some pretty sweet events. There is also a lot of other sweet little features like making a channel dark. By that I mean if you have say a channel with 50 people in it during an event or something and a mod needs to announce something to keep the event going. Boom 1 click only staff can talk, the rest of the channel is muted. Anyway, just my 2 cents.
