Which laptop to choose that will play 4K content?

Just a few years ago when buying a laptop we where concerned if it was capable of playing 1080p smoothly and at any bit-rate. Back in year 2007 playback of 720p and 1080p was not a problem for Core 2 Duo CPUs which dominated PC market at those days, but if you decide to play any 1080p content on YouTube with your old Core 2 Duo PC these days you will find out that it is just not working - frames are dropping, video is stopping for a second here and there. Your old laptop is struggling decoding H.264 and H.265 and other codecs used by YouTube to squeeze HD content and save bandwidth.

Introduction of H.264 and even more recent and aggressive H.265 codecs helped squeeze huge 1080p movies and make HD content up to 10 times smaller in size, saving disk space and internet connection bandwidth. But the price was higher requirements for CPU power for decoding content. As a result if you want smooth 1080p playback at any bit-rate and coded with any codec , you will need a laptop or PC made not earlier than 2011 or any laptop/PC which comes with i3/i5/i7-series CPU.

What about 4k? 4k is becoming very popular on YouTube and many cameras are offering 4k video shooting these days. Any Intel CPU designed starting year 2016 have a 4k native support. it means 4k decoding is implemented and optimized in these CPU's.
What if you bought a laptop made in year 2014-2015 , say Thinkpad x250 which is build around Intel i5 5200U ? It will be fine  - it will play 4k but since this CPU does not have 4k native support it will utilize more of it's core power to play 4k content and will stay at 70-80% of it's power occupied with the task of decoding and playing 4k video. Needless to say you will get more noise from fan of the laptop.