I use to have a Galaxy S5 for business purposes along with my 6 Plus but I realized how much it irritated me once the novelty wore off. When the new iPhones came out I gave the Samsung to my niece & bought a 6s & 6s Plus...couldn't be happier.
To me sticking with the same ecosystem makes sense. While I find it entertaining to play around with Android/Windows phones I can't justify having to deal with them on a day-to-day basis. Whether it be iOS, Android, or Windows, the devices are designed to work with each other. Two iPhones makes more sense to me than an iPhone and a Galaxy.