In May 2014, I did a video showing that the iPhone does NOT charge faster with an iPad charger. With the iPhone 6, there are claims that it does charge faster with an iPad charger, so here’s an updated video for the iPhone 6.
The claims are right. While the iPhone 6 draws ~1A from the iPhone and LG chargers, it managed to draw ~1.2 to 1.3A from the iPad and generic charger. So yes, the iPhone 6 will charge faster with an iPad charger.