Get updated to the latest android version 6.0 a.k.a android marsmallow. Here android has done a big change that solved problems of many.
Android users always worried about memory space getting short one day or the day but marsmallow got the solution for it, where almost all user installed apps are transferred to sd card along with their data and this helps you phone have more memory and even runs faster than ever as you phone memory goes more. You will really like this. So always follow the trend and go for the marsmallow.