well basically because the rocker is worth way more than two pairs of invaders.. only get the invader if all you want to do is ski rails and wreck your ski.. in which case i'd just get a second hand ski off someone for 50 dollars and mount them..I have skied both and the rocker is better in every condition.. Its lighter than the 178 invader, better in pow, better on piste (suprisingly), easier to butter because of the rocker despite being stiffer and more consistent.. its a seriously good ski.. when I have had a chance to ride it 10 more days i'll review it properly.. its in the running for my favourite ski ever.. previously line elizabeths which may also be an option..