Xiaomi Mi 3 and Xiaomi Mi 4 belong to Xiaomi's flagship mobile handset line, the high-end Xiaomi Mi series, with the Xiaomi Mi 3 being the flagship product before it was succeeded by the Xiaomi Mi 4. So how do they size up against each other? Which is better? Let's take a close, comparative look at the two smartphones.

The Xiaomi Mi 3 was unveiled during Xiaomi's New Product Launch Event in September 2013. It was highly anticipated. Upon its release in China, the company sold 200,000 units within 3 minutes of launch, and it sold out in India in matter of seconds with 100,000 registering regardless of the 20,000-stock limit, according to reports by Tech In Asia and International Business Times, respectively. These feats make the Mi 3 the fastest selling smartphone in Xiaomi's history.   

The Mi 3 puts a premium on speed. Consider its slogan: "Accelarate your life". Of course, the Mi 4 had to be better if it is to supersede the Mi 3. "The Fastest & Most Gorgeous MiPhone Ever", goes its slogan. So what makes these phones fast? Let's pop the hood and see what's inside the sleek designs.

The Mi3 features the relatively fast 2.3 GHz quad-core Qualcomm Snapdragon 800 processor. The Mi 4, however, is powered by the new 2.5 GHz quad-core Qualcomm Snapdragon 801, which is quite faster. Both use the Adreno 330 graphics processing unit.

Both smartphones come with Android 4.4 KitKat operating systems. The Mi3 uses the MIUI 5 interface, while the Mi4 uses the latest MIUI 6, which gives a more iOS-like user interface and other several features.

The older smartphone is lighter and thinner than the newer one, with the Mi3 weighing 145 grams and measuring 8.1 mm in thickness, against the Mi4's 149 grams and 8.9 mm thickness.

Both have 1080x1920 pixel display at 441 ppi (pixels per inch).

The Mi4 outlasts the Mi3 with a 3080 mAh battery pack. The Mi3 uses a 3050 mAh battery pack.

Both comes with 13 megapixel rear cameras, but the Mi4 wins the selfie contest with its 8 megapixel front camera supplanting the Mi3's 2 megapixel camera.

According to a report by Kpopstarz, the Mi3's 16GB variant sells for $270 while the 64GB version has a $320 price tag. The 16GB Mi4 sells in China for an equivalent of $320, while the 64GB variant goes for $405, added Kpopstarz.  

The Mi4 beats the Mi3 in many respects, but it doesn't mean that the Mi3 will be biting the dust. While the Mi4 is obviously more advanced, the Mi3 doesn't necessarily fall behind in terms of features and it is hugely popular with a substantially large market branching out from China to Hong Kong, Taiwan, Singapore, Malaysia, the Philippines, and India.  The Mi4 is just beginning to tap into these potential markets.