in case you still havent made your mind up, i'd start with 160. From what i know of the pikes, its easier to change them down to 150 from 160 by cutting the air rod than going the other way as you'd have to get a new air rod.
personally i have xfusion sweeps on my 2014 trance (rockshox monarch plus rt3 rear) left them at 160mm for a while, put a spacer in to go to 140, futzed around changing it between 140 and 160 for a while, now i have 150mm in there (10mm spacer) and it's good. I rarely say "I wish i had that extra 10mm", but at least i have the option of doing it. travel adjustment with spacers is pretty easy on the sweeps, thankfully, just need the right tools.
Going from 140mm up, i didnt really notice the difference when climbing, only on the steepest stuff that I'd have to walk up a lot of the time anyway. I dropped the stack height by moving spacers ontop of the stem and got slightly lower rise bars anyway, helped get a little more weight over the front.