How does HDMI cable 6 vary from cable 5?

There is no 5 and 6 HDMI cables unless it is referring to the length of the cable 5 or 6 feet. HDMI cables come in the categories 1, 1.1, 1.2, 1.3 and 1.4. The advantage of 1.4 is that it can carry 3D signals, ethernet and 4k pictures.