Reality is iPhone 6 series is just catching up to old Android phones like the 2012 Galaxy Note II that typically gets two days of use and up to six days of idle time and there are newer Android phones that easily surpass that like the Sony Xperia Z3 Compact.
http://www.gsmarena.com/battery-test.php3
I've heard that the Sony Xperia is good, but I find the UI pretty ugly. Personally, without paying attention to articles on the web, I have had better battery life on my iPhone 6 than the Galaxy Note 4. With that said, before I used my phone primarily for work, I used to root Android phones and squeeze out amazing battery life, but not so much without rooting.