i would say invaders, i love mine!
SPK's are stiff man, one of the stiffest twins that salomon has, they were built as a pipe ski
reno jibs are a stiff ski while invaders are soft. it isnt a question of which one is better here, rather do you want a stiff ski or do you want a soft ski. stiff = good for hitting big features and not washing out. soft = good for dicking around on, butters, presses, and a bit more forgiving. i would say that the fun factor on a soft ski is deffintly higher in terms of all mountain but stiff skis are better on big jumps.
ive never ridden invaders but i had a pair of reno jibs, they are very light and very poppy but they broke in 6 days which sucked..