I think it's what Bobby said at the end of S5, how Dean sometimes just doesn't take Sam all that seriously because he's the younger brother and Dean feels like he has to shield and protect him from everything but sometimes that just backfires and it makes Sam make bad decisions, too. They keep pushing each other away but they always come back to each other, too, and that's the clearest sign for how much they love and need each other. In the end, that's what it comes down to, right? And it's not about who's better and who's right because they get through things together. None of them could have stopped the apocalypse on his own, right?