The Inertia is a totally different reaction than the Widow. The Widow skates for about 45ft then turns over hard on a dime; almost no midlane read. The Inertia will give you a lot more midlane read and will be a lot more even arcing than the Widow. Also, from other accounts here on the Track board, if you dull down the Inertia, it can handle a lot of oil, so you have versatility there.
Personally, I dont think you could go wrong with any Track ball right now. They're all great and underestimated pieces. Also, I would sell the Widow and get a Power Machine. Exactly what I did and I havent regretted it one bit.
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Bowling Since March 2006 - "Get coaching, don't worry about it"...blah blah balh...Just answer the questions please
Mean Machine > Power Machine > Equation > Heat Blast