I've used the P1500 and P3000 grit ones. Because of the degree of change, there is a more siginificant difference, in ball reaction, going from 1000 to 1500 to 2000 grit, than there is gring form 2000 to 3000 to 4000 grit. Other than that, finishing a ball using those grit levels does just what you'd expect. It is so easy with a little bit of water and a few seconds on the spinner.

The biggest change is using the FEPA graded  pads versus the CAMI pads solelybecause there is a much small variation in the FEPA grading system. That is, if the abrasive size is too far from the average as specified by the pad number, it's not allowable on the FEPA pad but is allowed on the CAMI pad. So if you use, for example, a 1500 grit pad, you get 1500 grit within a smaller range of error.
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"None are so blind as those who will not see."