Buried under the piles of footage we took with this year's iPhones, a comparison between the video output of the iPhone 6s and the 6s Plus somehow managed to go unpublished. Well, that changes here and now. OK, actually we added it to both reviews yesterday, we're just making sure you're in the loop. So, as you can imagine, everything else being equal, the VS focuses on optical image stabilization. The iPhone 6s doesn't have it, and the Plus does. Where the iPhone 6 Plus only used it for stills, starting from this generation it's also employed when shooting video. And it makes all the difference in the world. Building on top of the already capable electronic image stabilization of the iPhone 6s, putting the hardware to good use yields even better results. You don't need to trust us on this one, watch it for yourself in the video...
Source: http://www.gsmarena.com/stabilization_test_iphone_6s_vs_iphone_6s_plus-news-14770.php