The farther the pin is from the pap the farther the ball will travel before giving up it's rotation, the 10:30 position makes the ball give up it's rotation more quickly than a 12:00, meaning it will have a sharper move, but get into a stronger roll after making it's move, the term hook/set has been used to describe this reaction. Putting the pin below the fingers is used in this type of drilling to help the ball react sooner or putting the pin above the fingers to make it react later. Bowlers with 75+ degrees of axis rotation (like Pete Webber) are benefited by this pattern because it helps the ball get into a roll before the ball hits the pocket. Most bowlers can use this pattern on a fresh oil pattern.

A stacked (or 12:00) position makes the ball retain some of it's rotation after the initial move and make a more continuous hook in the back end this drilling is good for carry down as the ball will still have some energy left to cut through the oil on the back end.

A 1:30 drilling makes the ball retain it's rotation the longest and makes the ball have more of an arcing type move because the energy of the ball is spread through out the hooking motion of the ball. This type of pattern is good for  shorter oil patterns and players with high rev-rates.

Hope this helps.