0.5 ohm (subohm -under 1 ohm) is for lung hits, inhaling straight into you lungs.
1.5 ohm is used for mtl (mouth to lung). Similar style to smoking cigarettes, into mouth and then down.
0.5 uses higher wattage than 1.5 and drains battery faster.
0.5 should be used with 0-6mg juice
1.5 any mg.

0.5 will provide alot more cloud and flavour however a higher nicotine 12+ will be giving you throat hits
1.0+ if used on the same subohm tank this’ll still provide just as good a vape but reduce the nicotine throat hit

(Experience from KangerTech SubTank V2/PLUS 0.5/1.3 coils)

The difference in resistance relates to how they respond to power. The 1.5ohm coil will heat up faster and require less wattage than the 0.5ohm. They are designed for different vaping styles with a subox, the 0.5 will be for large volume vaping (clouds) and direct lung inhales with the airflow opened wide, the 1.5 will be more for vaping like you used to smoke where you inhale into your mouth and then take it into your lungs and will work better with smaller airflow. Note the wattage range that kanger gives you on the coil and the card in the kit, as a general rule start at low wattages and work your way up slowly until you find a satisfying vape. Make sure to read through the info in the kit as it shows you how to get set up properly. Enjoy!