it depends on how your ball is laid out.  my oi is drilled as an early roller with the pin beside ring finger and the the cg 3 inch below and slightly to the right (out of box condition). my si (pin under ring finger with cg 2 inch below slightly to the right (also out of box) is more aggressive.  on med dry, my si allows me to play from 20 to 8 - 7 boards back into the pocket.  my oi on the other hand, if playing the same line, goes a little longer.  for me i guess it's a matter of preference. but for sure as the lanes gets more dry, i pull out the OI for this reason...
 
and i qoute: " the OI is the most versatile ball i've ever owned". money ball.

                                 
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Inferno Bowler: "Throwing a strike when the game starts is only a minor obstacle. Throwing a strike when you really need it in the 10th frame can be a whole different beast"   Parker Bohn III