Out a thru-hull.
If you run it into a stanchion, it'll cause you nothing but problems...'cuz the slit in the stanchion will clog up regularly...even when it's not clogged, there's so little air exhange that odor is inevitable. My advice: use a 1" vent line, which will require using a 1" thru-hull instead of a "vent fitting," and make the line as shot, straight and horizontal as possible.