Feel free to add your own favourite if it's not there.

Personally, I feel Hermitcraft is thriving, and will continue to do so well into the future (particularly now that Etho and docm77, two of the biggest minecraft names, have joined). It has a highly active community with amazing builders (falsesymmetry, slipg8er, etc) and amazing technical-based players (xisuma, mumbo, tangotek, etc). Overall it seems the most enjoyable to watch at the moment.