The Premium comes in a cool cart. It has a higher resistance (3.3 ohms) and the cart and vapor stay a little cooler. The Wow comes in a wow cart which has a lower resistance (2.2 ohms) and the carto gets a little warmer and has more vapor production. They are also made with different recipes, so they taste slightly different. To me, the Wow has a stronger coffee taste.
ETA: Oops, we crossed in cyber space.