I just did more testing with using vibration as a sensory method and found it's probably your best tool for accuracy when ryhthym and reaction time for the lower tier cuts. Since the tone and vibration are slower and longer coinciding with the speed of the spin, it's just a matter of timing the cut just about when the vibration ends. So essentuallly the tone and vibration are basically there to let you know that you should be ready to cut after the tone and vibration. I also find it easier to react to touch than sound. This is probably because touch seemss almost instant for me to register, and sound as fast as it is takes me more time to register.
Okay, I am 100% sure that you will get best results with the split tap gesture while using both the tone and vibration to time a lower tier cut. I got my highest cut today without counting and without anything but pure reaction to sound and touch. Just use the start of the vibration as the signal that you should be ready to cut very soon and you should be cutting gems in the 90's. However, you should probably continue to use the double tap gesture for higher speed cuts on higher tier gems because for some reason it just seems to time up perfectly with it, much more than the split tap.