First I thought 'how cool, they already have the new mobile device resolutions included in their dialog box when opening a new PS-document' to find out a moment later, that the iPhone 6 Plus' resolution is wrong. In the dialogue it's 1080x1920, Full HD, which actually does apply to the display's resoliution, but not to the software. The software needs to be rendered at 1242x2208 and scaled down to 1080x1920. It's not documented too good and many sourced like Wikipedia actually got their numbers wrong. But owning an iPhone 6 Plus and currently working on a Retina HD version of an app I have to deal with exactly this issue. If you throw a 1080x1920-Image into the iP6+, it gets scaled down, although it would fit according to it's screen. Strange thing though.