I believe this can't be understated. I keep bouncing out to Chrome and Firefox, and then back to Safari. Chrome burns CPU (and batteries) like it's going out of style, and Firefox just can't keep up in the performance space.

It's telling when hangouts in Safari takes up less CPU (and performs better) than in Chrome.

Regarding WebRTC: I've not run across any usecase which requires WebRTC to this day - everything I do with web-based communication is one to many, necessitating something like Google hangouts or Skype for video or audio, and Slack/Hipchat/IRC for IM.