Replying to Moment Night Train / Armada JJ Ski Size

So i'm considering either of these skis as a Pow ski. I'm 18 years old, 5'10", and 135-140 pounds (yea i know i'm really small), i currently ski on 172 line Blend (the old, gold ones) and am wondering about weather i should stick with a ski around 170, or get the 185 (or whatever the equivalent length option is for these skis) I heard that skis like the JJ ski short because of early rise tip/tail,  and the 180 would be more like a 165... so given m weight should i go with the 180 in either of these skis or should i stick with the 175?