The Fat Cat 6 is awesome. It states it is capable of carrying 6 fat skis or 4 snowboards, which is true, and then some. I have been able to fit 4 snowboards and a pair of fat skis next to them as well. It's sleek, doesn't have that annoying whistling noise when you are driving and I haven't seen it affect my gas mileage yet (That is based off of driving with no skis in the rack). My previous one lowered my mileage by 3-6 mpg. Definitely worth a little extra money because it will pay you back in better gas mileage in the long run.
I really like the overall design of these board racks, being the engineer it was pretty straight forward to mount and install them once I read the instructions. My one recommendation is to just go with the black model and not get the color matched panels for your car, I have a standard silver car, and the gray/silver that I got is more of a taupe/tan. I am pondering spray painting them