From my little experience I've found the disposable blade more rough. Jagged looking on the edge when looking at magnification levels. I think that straight are much smoother edged.That plus I'd say the issue is too much pressure on one side like others have said. Another issue is he most likely doesn't do shaves daily like barbers used to do. Not enough day to day practice. But he was plenty happy to do it when he found out you was willing to pay the funds. Its not his mug he's working on.