the 3rd one, Has a 980m gpu, Itll easily surpass the first 2 by a noticeable margin in gaming, as the 960m is just not cutting in games these days at 1080p.
Skylake is around 10% better then Haswell. So the difference is that noticeable. Though Skylake CPus use less power so thats a bonus on laptops. Also if its using a skylake cpu then it probably has a better gpu aswell.