I had a play with a pi 3 recently. I quickly tried Firefox and Chrome and they were hopeless for decoding YouTube even at low res. I worked around by downloading the vid and then using a pi video player. Not a problem.
So is pi hopeless for streaming YouTube? If so that is ok. It is not an issue.
Or did i miss something obvious? Maybe hardware acceleration in Chrome?
Edit: it was running the recent pi mint distro, wifi.