My wife and I usually watch a Netflix movie on my wifi iPad by the San Diego bay in Coronado on date nights, but for some reason, we were watching silly song cover vids on the YouTube app and couldn't stop laughing some of the youtubers. The videos loaded fast, and was very clear on my wifi iPad. The location also has very good Verizon 4G LTE signal, so I think it has to do with the internet connection. There was one YouTube HD video that I was trying to watch in the car, on the way to Coronado, on a 3G signal... and the YouTube video stalled badly... and wouldn't load. When we got to the Bay, the same YouTube video played with no stalls and was very clear on 4G LTE. I can't be certain if it's iOS, but video's seem to be fine if my internet connection fast.