If you are streaming videos from Youtube I do know that depending on site traffic and the channel you are watching may have some lag. I experience that and so do others on other ISPs, especially on high qualities.
Yeah that's why I tested on numerous channels. Swamping resolutions netted the similar speeds. I know sometimes I see huge download speed differences just swapping resolutions. Not in this case. In the end when this happens I can't even watch a 360p video on my cable connection without constant buffering and yet cellular connection does fine during these times. 'Site problems' shouldn't be connection specific.