iPhone 6 and 6 Plus Responsive Breakpoints [duplicate]

Answer 1

You're referencing the physical pixels of the device, rather than the css device-width sizes. According to this tweet, the device-widths for the two will be:

iPhone 6: 375px (2.0 DPR)
iPhone 6 Plus: 414px (2.6 DPR)

Knowing that (and assuming the tweet is correct), and assuming your using the proper meta viewport tag, you're looking at roughly:

iPhone 6: 375px (portrait), 667px (landscape)
iPhone 6 Plus: 414 (portrait), 736px (landscape)

Hope this helps!

Edit:

Regarding the 2.6 DPR of the iPhone 6 Plus, it's actually 3.0 DPR downsized by 1.15, which results in 2.6 DPR. More info can be found at http://www.paintcodeapp.com/news/iphone-6-screens-demystified for clarification (thanks @mdcarter for the link!)

Answer 2

@media only screen and (min-device-width: 375px) and (max-device-width: 667px) and (orientation : portrait) { 
    /* iPhone 6 Portrait */ 
}


@media only screen and (min-device-width: 375px) and (max-device-width: 667px) and (orientation : landscape) { 
    /* iPhone 6 landscape */
}


@media only screen and (min-device-width: 414px) and (max-device-width: 736px) and (orientation : portrait) { 
    /* iPhone 6+ Portrait */
}


@media only screen and (min-device-width: 414px) and (max-device-width: 736px) and (orientation : landscape) { 
    /* iPhone 6+ landscape */
}

@media only screen and (max-device-width: 640px), only screen and (max-device-width: 667px), only screen and (max-width: 480px){ 
    /* iPhone 6 and iPhone 6+ portrait and landscape */
}

@media only screen and (max-device-width: 640px), only screen and (max-device-width: 667px), only screen and (max-width: 480px) and (orientation : portrait){ 
    /* iPhone 6 and iPhone 6+ portrait */
}

@media only screen and (max-device-width: 640px), only screen and (max-device-width: 667px), only screen and (max-width: 480px) and (orientation : landscape){ 
    /* iPhone 6 and iPhone 6+ landscape */
}

You can get list of media queries for all standard devices here