The XL is not urethane its xtra length pearl reactive, The XXL is pearlized urethane but acts like a pearl reactive to me.  The XXL did not roll like a urethane and to me they are very similiar in reaction and I have thrown them side by side with the same drill.  I would say the XXL does go a little longer and snaps a bit more than just the XL.  They both are now discontinued.
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I should just quit bowling, oh wait I already tried that.
Now that I am back and my Saws are sharp again, I am ready to cut some wood.