AOSP!!!!!!!
To me, less is more, so i choose AOSP. I've tried MIUI 8.2, the battery is good enough (4-5hrs), but the ram management is bad, I don't feel like I have a powerful device on MIUI 8.2 because the apps load kinda slow same as the wifi (max: 1mb/s) and my country 3G is bad on MIUI...