Without including framing - at which Posey is like best in the league category, to the benefit of Bumgarner - the latter has only out-WAR'd the former twice: once in 2011 when Posey was out for the year and once in 2016. Posey also projects for over a win better, and again this is without factoring in framing. It's pretty clear to me that Posey is the superior player, and always has been.
That's right, I put my Grant boots on for this one.