Accessories and gear
Even though YI’s price tag is lower, SJ4000 comes with lots of additional gear and mounts that you can use to attach your camera to different things. Xiaomis product comes only with USB charger, where as SJCAM insersts plenty of additional accessories you can use.
Having gear is important if you want to attach cameras on a tripod, head, chest, wrist or even a dog. While not all accessories that are inside the SJ4000 box are useful, you will find them pretty cool to have. Check this article too see kind of accessories available for SJ4000.
Xiaomi YI requires some of investment in gear. For instance only original waterproof case is priced at around 30$. Good news is that both cameras are compatible with most GoPro type mounts, bases and clips.
If you are type of person who needs all these stands, bases, mounts and waterproof case for under 100$, SJ4000 is certainly a better option. If you would like to purchase all the SJ4000 gear separately, it would cost you at least 30$. Have that in mind when comparing prices of these cameras. Xiaomi priced their camera lower, but they certainly will be making most of the profit on gear which has to be bought separately.