Replying to Armada JJ Length Question

I am going to be getting a pair of Armada JJ's because the shop near me has a great deal on them. I am torn between getting the 175 length or the 185 length.
I currently have a pair of line anthems at 171 that I used every day last season.

Height=5'9-5"10
Weight=145+/-
Ability=Expert
Local=East coast
Days Riding=3/4 days per week opening day through closing day

I will be using the skis primarily on our east coast powder days and will be spending most of the time in the trees.
An employee at the shop was telling me to go with the 175 length cause it would be more nimble in the trees, although I know with the rocker a 185 length could feel closer to a 180 or even less.
So what would you suggest and why?