Some phones just can't be reviewed in a vacuum, the competition between them is so fierce - and their price tags so high - that they have to be compared against each other under a microscope to determine the best one for you. The Apple iPhone 6s and Samsung Galaxy S6 are joined by the Sony Xperia Z5 for this three-way fight.
Source: http://www.gsmarena.com/iphone_6s_galaxy_s6_xperia_z5-review-1330.php