The base is completely different, it still features four contact points, but now it’s easier to adjust the stance and the it’s thinner for better transmission to the board.
The new Prime system features a lever on the back of the binding that tightens the binding in riding mode, while it also locks the heel if you need to skate ski in rolling terrain.
The heel risers has been also redesigned so they are easier to reach with the basket of your pole, and at the same time they are wider for improved performance when traversing since there are more contact points. The new Prime system offers a superior board-binding connection that feels like riding a solid board.
Check out the video from Chad Perrin from Karakoram explaining all the details about the Prime system.