I have played with anything from a Lepro to a Kamui soft, and in my personal opinion, I have never been able to tell a difference in the amount of spin created from either tip. I do think it feels a little different, but the results have always been the same, and please understand that there was no bias involved. I fully expected the Kamui soft to spin the ball more, but it just didn't happen. Maybe that comes from a poor stroke in general. I don't claim to be a great player, but I can draw the CB the length of the table when needed. I would say that it has become my anecdotal opinion that different tips don't spin the ball more than others, and now science appears to back that up. I am not looking to argue or suggesting that I can't be wrong, however every shaft and tip that I have been told will spin the ball more has never done so, and so far that has been backed up by science.
Spin appears to be dependent on two things: the accuracy of your stroke, and a well chalked tip. A quick review as stated by Dr. Dave is listed below for anyone interested.
Dr. Dave:
There is no question that a harder tip "feels" different and provides different "feedback" (a softer tip typically dampens the impact a little and the force of the hit isn't felt as strongly). It is also true that a harder tip can result in a more efficient hit, providing more speed to the CB for a given cue speed. And it is true that with slower CB speed, more backspin will wear off on the way to the OB with a draw shot and more sidespin will wear off on the way to the cushion with a sidespin shot (especially on slow and sticky cloth with slower shot speed). These effects might make it seem like a softer tip is applying less spin to the CB. Regardless, the quality of spin (i.e., the spin-speed ratio) delivered to the CB depends only on the tip contact-point offset from center. The physics on this is very clear. If anybody doubts this, they should do a careful and objective experiment to compare any tips they think would produce different results. For those who have math and physics backgrounds and are interested, the physics showing how the spin-to-speed ratio depends only on tip offset from center, even when accounting for tip efficiency, can be found in TP A.30 - The effects of cue tip offset, cue weight, and cue speed on cue ball speed and spin.
Some people think that because a soft tip stays in contact with the CB slightly longer (see contact time), a soft tip can apply more spin. However, see Bob Jewett's comments below. Also, the contact time is still extremely small with both a soft and hard tip: close to a thousandth of a second (0.001 sec). Assuming the CB speed is the same in all comparisons, even though the peak force will be different (more with the shorter contact time), the amount of momentum (linear and angular) transferred to the CB will still be the same (because the sum of force over contact time is the same in both cases). The CB doesn't move much (translation or spin) during the extremely small contact time, so the only significant factor is the tip contact point at impact.
Now, it is possible that a hard tip, especially if it is not holding chalk very well, will have a smaller miscue limit than a soft tip that is holding chalk well. In this case, the soft tip will enable a player to apply more spin to the CB since the tip contact point can be farther from the CB's center without resulting in a miscue.
