The WS6 package gets you the hood, a different lower airbox, bigger sway bars, 17" wheels, a 3" (vs 2.5") catback, and a badge on the back. I am not 110% sure, but I think you get different exhaust tips, too.

Between the airbox and the exhaust, it's supposed to rate you another 10hp or so.

 

I had one, they are overrated.......lol j/k as Dino stated is the difference mainly, are you looking at one?