Apple device are popular nowdays as some are buying for showoff or some buy for satisfaction
before buying any apple product you must know that apple ios is closed system so will not be free as using android but instead u get realibility and satisfaction iphone 6s and 6looks are similar but there are some distinct feature that are not present in iphone 6
some specs reminder
iphone 6- 8mp camera
iphone 6s -12mp both are good but while zooming 6s is better
one the fun feature is live photo and 3d touch in 6s u can also shoot 4k video and its awesome , some people are concern about battery life but as I am using both device 6 and 6s , u can easily go through a day standby mode is just awesome if keep it like 69% battery u will get the same after an hour so dont worry if u want more juice buy the bigger 6s plus
Nowdays ios 9.2 is the current version which is improved update than the ios 9.
if u want to buy this phone go for it u will never go back again to other device