Have done up a bunch of Wow Pearls in our area and they have done well. They see to work well on heavy-mediums. Just like any pearl though they can ping corners if angle is wrong. They seem to react favorable to hand adjustments and good versatile ball. The threat goes much longer in my opinion and does a hard rush on the end. I believe this ball suits medium patterns better. Due to its length again angle is crucial to carry.

Due to the varability of people talking about conditiond this is my breakdown of patterns we see in our area and chracterization for equipment

Heavy oil - Dull particle or Dull agressive reactive
Med-heavy - particle both sanded or pearl, agressive to medium agressive reactive
Medium - med reactive shined or pearl reactive, agressive urethane
light-med - weaker pearl reactives, medium strength urethane polished or dull
light - very weak reactives, pancake weightblocks, polished urethane

Hope this can help a bit, again factors such as speed and revs also should play a part in your choice. The threat could cover a slightly heavier pattern with surface adjustment and high revs.