I have a Hornet and have seen two co-bowlers (one @ Nationals and the 2nd, I bowl with in the Summer) use the Neptune. The Hornet handles more oil. Strong pin Neptunes (3.5 - 4" pin to PAP) can hook a lot. Pins at 5" and 5.5" need a LOT of dry to hook, to turn the corner. The Neptune is more of a light oil ball than the Hornet, which will handle light oil but then it will have more backend and overall hook than any Neptune.
FYI I use a Blue/Green Centaur as my lightest oil ball; it fits under my Hornet.
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"None are so blind as those who will not see."