Choosing between a straight or coiled leash usually involves the style of paddling you normally do. In the surf you want the board away from you. A straight leash at least as long as the board so that you are safe as you get pounded by waves. For touring and racing, a coiled leash keeps it out of the water and minimizes drag and keeps it close so you can quickly rejoin the race. A coiled leash is also great for general flat water paddling as it stops a lot of tangles around your feet and other items. A straight leash is more traditional and therefore many are more comfortable with a straight SUP leash.
VESL Straight Paddle Board Leash