I started out using the black-cased Wilkinson Sword razor blades. They're made in Germany and seem like pretty high quality blades. However, I found them to be very inconsistent. people rave about WS blades, but I just don't think they're all that great. I find some to be very sharp, and others to be very scratchy, even from the same pack. I have used these, Shark Super Stainless, and Derby Extras. Out of these three contenders, Derby wins hands down. How did they work for you, and what is your blade of choice?