Battery and memory card
Both manufacturers recommend that you use reputable class 10 microSD or microSDHC cards. Xiaomi YI supports up to 64gb cards, where as SJ4000 can handle 32gb. SJ4000 has 900 mAh, where as Xiaomi YI has 1010mAh battery. Also, because of the fact it does not have a screen, YI consumes slightly less power and provides longer battery life.