I like S3/B2 because the vendor only ever sees encrypted bytes. All decryption/plaintext is on the device. YouTube does not get you there. In fact their entire model is predicated on watching your every move.

As far as Peertube, I don't know enough about it. If I put a massive-bitrate video in some weird format on it, and then try playback on a crappy phone, will it work? If I go through a short tunnel, will it buffer or degrade quality gracefully? I don't want to worry about it.