The biggest diff visually is the PJ has an oval slide and the PWK has a D-slide, but both are still considered "flat slide" carbs. The PWK is a newer design and has more high-end flow and power. The PJ is better for low end. Both can be made to work with a little time and patience.
PWK is available in a wide range of size, 28-39, while the PJ comes in 34 and 36.