The "V" Wedge Notch or Saddle Notch is one step above the now outdated "round notch". The "V Notch" is the most common notch used in the industry, and if properly overscribed, the potential for gaps is reduced considerably.
The "Diamond" Notch which is a "V" Notch performed on both the top and bottom, is typically used for high-end homes. The Diamond Notch requires approximately 15% more production time. It's considered the premiere notch in combating shrinkage.