156 at B16 is actually bigger than at G14, since all of the area around K14/J13 is probably dame trash anyway.
One of the things that makes B16 bigger is then W can play A18. If he does, then B has only one eye in the corner and must kill the white stones at G17/G18 - or at least be ahead in the liberties race to do so. That is about 4 stones that B must play in his own territory to defend against 2, a net profit for white.
So to avoid that situation, B plays A18 himself - in gote.