YOur benchmark ball is the one IN YOUR MIND and in your hand in which you have the most confidence to use to tell you how the lanes are reacting when you know nothing about them. It should give you a feel for the oil pattern's reaction and how to play it in 2 or 3 tosses. It should also tell you very quickly whether you need a different ball to play them corectly.
In general, they're medium finished, solid resins or particle pearls which you'd normally use on medium oil. NOrmally they are control balls with neither a small hook nor a huge one; they are arc-ing balls, never skid/flip type balls.
Most people, I believe, if they had to choose from your selection, would pick the Classic Zone or the Ace, BUT, depending on their surface finish, how they're drilled and how you throw the ball, both of these could be very flippy reacting balls.
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"None are so blind as those who will not see."