Marketing department wins!There is no 15% delta and no battery gains. The only gain you will see is in the IGP (integrated graphics). The CPU share the exact same micro code and architecture as Skylake. It has the exact same IPC, so the only difference is a slightly optimised production node going from what Intel is calling 14nm to 14nm+. This gives you 100MHz higher cpu clock speeds at the same TDP. That's it.
There's a reason why a Intel Core i7-6700K and Intel Core i7-7700K at the same clock speeds gives more or less identical performance. It's because KabyLake is just Skylake rev2.0 and nothing more. But people keep getting fooled by the naming and tells themselves that it has to be better because it's newer and got a new name...