If you are young and starting out with DE shaving, Derby Extra blades might be just the thing. However, for those who get back into DE shaving after years of using electric shavers or cartridge razors, Derby Extra might not be suitable due to changes in beard hair and skin as we age.
For many folks the Astra SP blades work well. However, my beard hair has gotten so tough that Astra SP blades are barely sharp enough to cut it. There are so many variations in beard hair and skin type that it is a good thing we have lots of DE blade alternatives.
(Say it like Joe Piscipo in Johnny Dangerously) 
