In the extreme, it's easy to conclude that a cue tipped with a sponge would drive the ball forward with notably less force than one tipped with steel even if both struck with the same speed. Phenolic tips will transfer more force (though will be less forgiving of an inaccurate stroke) than a hard leather tip, which will similarly transfer more and be less forgiving than a softer tip.
The real question whether you'll realize what you will perceive as an effective difference, and that is something that depends largely on your personal breaking mechanics.
I haven't ever simply replaced a leather tip with a phenolic to be able to give opinion as to what replacing that sole component resulted in for me, but can say that the difference in using what I had been using to break (Schon 18.7 oz with a Tsunami extra hard layerd tip) going to a Poison VX BRK (19 oz) with a phenolic tip is, to my perception,
very substantial - though it's worth noting there are number of other differences in construction which surely make their contributions as well. I haven't used any tools to measure effective mph, but the resulting breaks appear to indicate some net gain - provided you maintain absolute accuracy and don't go for heavy spin (phenolic doesn't offer much tolerance for off-center hits).
Haven't tried it myself, but I believe
this is the site of the app referenced (
iPhone/
Android).