I've tested over a dozen highly shaped poly strings in the last few months and the strings with the absolute highest spin capability are Grapplesnake Cube, Volkl V-Square, and Volkl V-Torque. Have not yet tried Ultra Cable, nor have I tried V-Torque Tour. Have tried Hyper-G, Tour Bite, and Revolution and Cube/V-Square/V-Torque all have better bite on the ball, especially in skimming type shots, but these three also have major downsides, being playability duration, notching/breaking, and tension loss, respectively.