Why is this You Tube video sharper than my iTunes purchase?

Here's two screenshots of the same video. The one on the left is from You Tube and the one on the right is the one I paid for on iTunes. Why is You Tube video sharper than iTunes purchase?

These art not Album Art. They're two screenshots from the videos. I noticed the iTunes video was grainy and soft, so I paused and took a screenshot of both You Tube video and iTunes video. I assumed buying the video would provide a clear video, but the free You Tube video is noticeably clearer. Any way to fix this? Is this normal?