One Life Sizing

I'm looking at buying this years One Life's and took a look at a few threads about them and still can't decide which size would be the best fit for me. I'm 5'10, 150 lbs. and I'm skiing mostly Tremblant this season but will be living out west for all of next year. I already ski on a 181 AR6, and was wondering if it would just be the right decision to go with the 189 especially if I'm going to be taking it on groomers on the east for a bit, especially because you get extra running length.