They are not polar opposites. First, they are both mainline churches, which means that most of their theology comes from Biblical exegesis that is interdenominational. Second, even traditionally the differences are exaggerated. Wesley was a classical Arminian. Arminius was a Reformed theologian, differing only on details of TULIP. To some people this looks like a big deal, but it certainly doesnt make them polar opposites. And todays PCUSA doesnt really teach TULIP anyway. (We modified the Westminster confession in 1903 in a way that made it a lot closer to Arminius, and there have been more changes since.)