Ric,

Well, I've thrown all 3 and here is what I can tell you: For me, I could easily have found places for all three in the same arsenal. The Lives can either be a heavier medium to heavy, not flood, ball, depending on your speed, revs, and the coverstock prep. The Au79 is a good ball for opening up the lanes on standard to slightly heavier mediums with good backends or just a small touch of carrydown. It starts up earlier in the midlane than most pearls, but it also kicks harder on the back. It is a very angular ball that flips and just keeps on charging. It can be a tricky ball until you get used to it, but once you get comfortable with it it can be your first out of the bag on standard mediums. The Thing Returns, for me, was a great choice for lighter mediums. With my speed, and the drilling we used, I was able to get the ball down the lane with ease before it would rev up and come rocketing back toward the pocket. Now, a lot of people claim that this ball is much too strong for lighter mediums, so maybe it was just my higher speed that allowed me to use it for that. Nevertheless, I never had a problem getting that ball long. Well, those were my experiences with the balls in question. I hope that helps you at least a little bit.
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I can't bowl 300, but I can bench 315 : )