Uverse YT issues.
I had Uverse 29/2 (VDSL, but they allowed me to use the entire capacity of my line since I did not subscribe to tv or phone.)
But it seemed like most of the time that I wanted to watch a YT video, it would flatout refuse to stream in 1080P, I usually had to downgrade the stream to 480P to get playback without buffering.
Since I swapped to Comcast (Trust me i'm not proud to be on Comcast) My YT streams perfectly most of the time.
I understand that It may not have been AT&Ts fault, but in my area, comcast just handles youtube better.