If staying within Storm/Roto Grip, the Hyper Cell Skid is probably the best choice. It's a versatile ball that uses a proven core and offers a predictable motion downlane.
If looking within EBI, I would strongly recommend the Paradox. I've been very impressed with that ball. The combination of the unique motion it offers combined with the proven core and hybrid cover allows it to be versatile and handle a wide range of heavier and longer patterns. Dave81644 is correct in that it rolls more like a symmetric would. But, that is a good thing with this ball as I have yet to see the ball die out in back as can happen with high end asymmetricals in a lot of cases.
