my information is that M3's single core is 15-20% faster.
That would give it GeekBench 6 SC scores of ~3150–3300, which would put it above the fastest processor currently on their SC chart, the power-hungry i9-13900KS (~3100). Though by the time the M3 is released, the i9-14900KS should be out, and it's expected to be ~10% faster => ~3400 (and probably consume even more power!).
On the desktops, I'm hoping Apple will be boosting the clocks on at least few of the CPU cores on the M3 (akin to an Intel turbo boost). We shall see.
Also wondering whether M3 will incorporate either LPDDR5x RAM and/or PCIe 5.0.