I go for 2k7 because of editing limitations on my hardware. On my 2016 laptop ( I7, 16GB mem, fast SSD, NVIDIA Quadro M1000M) editing (hitfilm or Davinci) until 2K7 is quit fluid. 4K becomes really slow. And actulaly... I don't notice the difference on my 4K screen playing back 2k7 or 4 K from...