Board Thread:Wiki Discussions/@comment-24853432-20140423062926/@comment-26302001-20140429210552

Kakashi is the only foreign Sharingan User who has awakened it from 2 tomoe to 3 tomoe then mangekyo, so it was attuned better to his body despite the extra chakra usage. I don't think any other non Uchiha could be better with it, or use it better than him.