The iPhone 6S is marginally thicker. This material is 60 percent stronger than standard aluminium, but just as light.The iPhone 6S is also the easier phone to hold, thanks to its smaller size and metal back. The Galaxy S6, by contrast, is a slippery little sucker thanks to its glass back. Don't even think of laying it down on a slightly angled, non-grippy surface, as it has the tendency of sliding off with minimal provocation.Simply, the iPhone 6S display is smarter, but the Samsung Galaxy S6 screen is better looking.