I ride the 138 and I am about your size exactly (5-9, 160), but my wife is an advanced rider and she rides the 138 too(5-5, 130lbs). My wife sizes up, but I don't.
Truthfully, I was torn too, but settled on the 138. No really good reason other than I usually ride a board around a 138. If you usually ride around a 138--you should stick with it for the Company. I would not size-up just because the board has a little flex.