chronics are really good skis man. i have a pair of the 04/05 chonics and i loved em. there my rail skis now and theyr still holdin strong. the chronics are one of line's most durable skis.
oh and if you ski mostly park, id go wit the 170's
if you ski more all mountain, trees, occasional BC, id go with the 181's
get em bro, you WONT be dissapointed.