Chrome has Web Audio, which is pretty far from coming to Firefox, and seems low priority. That's why we keep seeing cool audio stuff posted here that's Chrome-exclusive. Firefox supports its own Audio Data API which predates the W3C standard, but it's deprecated, and will never be supported by other browsers.
Web Intents is another cool feature in Chrome that's not even on the map for Firefox. Instead there's a "counter-proposal" called Web Activities that no one outside of Mozilla is talking about (and it seems pretty dead).
I still use Firefox, but the lack of leadership in these two cases is discouraging.