That 1.3 GHz Core M chip will boost to over 3 GHz for short periods of time. It will perform very similarly to a Skylake i5 in tasks like web browsing, but will throttle aggressively under a sustained load. That's where the 1.3 GHz number comes from.

As for the new Skylake i5 - Iris graphics are a huge step up from the 4100 model, but overall there isn't much reason to upgrade. CPUs have been stagnating in terms of performance for a few years now.