With the Xiaomi Redmi Note 4 that launched in India yesterday, Xiaomi was pretty upbeat about their decision to launch a version of th phone with the new Snapdragon 625 processor. To Xiaomi the Snapdragon 625 is an upgrade over from the deca-core MediaTek Helio X20 processor that is found in the Chinese variant. Intriguingly, Xiaomi also considers this to be an upgrade over the Snapdragon 650 which was found in the Redmi Note 3 which according to the company sold like hot cakes last year in India. However, many view this as a downgrade largely due to the fact that the Snapdragon 650 has twin ARM Cortex A72 cores which are faster than the A53 cores found on the 625. Theoretically, this is a solid argument, but if one dives deeper, there is merit to what Xiaomi claims and it shows up even our review of the phone.

Faster cores don’t always mean they are better

The Snapdragon 650 has a six-core setup which consists of two Cortex A72 cores clocked at 1.8GHz and four Cortex A53 cores clocked at 1.4GHZ, effectively employing ARM's big.LITTLE technology to distribute performance efficiently. That was Qualcomm's first foray into providing a custom setup and as seen on the Redmi Note 3, it worked wonders.

Yet, since the Snapdragon 650 was built on a 28nm architecture without FinFET transistors, it resulted in using not only more space inside phones it powered, but also drained the battery faster especially when the powerful A72 cores were being used. This is because the 28nm process uses a 2D channel to channel power through the gates that results in leakage in power. This also results in the phone getting heated up faster.

The Snapdragon 625, on the other hand, uses two quad-core clusters of Cortex A53 with the power cluster clocking max speeds of 2.0GHz. Qualcomm achieves this by using Samsung/Global Foundry's 14nm FinFet assembly process leading to 35 per cent lesser power consumption over its previous generations. Also, the FinFet transistors uses 3D channel that protrudes out from the surface, with the gate wrapping around the channel from all three sides minimising the power leakage even when the cores are not in use. In that sense, the Snapdragon 625 is definitely the faster and cooler sibling of the two.

You can think of the Snapdragon 650 like a Honda Civic with a small nitrous boost, while the Snapdragon 625 like an Accord. The Civic will go faster when the nitrous is engaged for that short while, but overall the Honda Accord has the better and faster engine.

The 650 has indeed twin faster high performance cores, but due to the 28nm older manufacturing process and the lack of FinFet transistors, it will heat up faster and guzzle more battery. It will have that boost for a short period but a phone like the Redmi Note 4 wouldn’t be able sustain that level of performance for long without overly heating the phone or draining its battery quickly.

The 625 thanks to its 14nm FinFet architecture is more efficient. It can run at its top 2GHz clock speed for longer and without heating up. While doing so it will also not drain out the phone’s battery.

Xiaomi was gunning to make a phone that did exactly that as it wanted to reduce the size of the phone to 8.3mm and it didn’t want to increase the battery life by much and it wanted a boost in performance. That’s why the Snapdragon 625 makes so much sense. And if you think about it, there aren’t many phones in the market that utilise the Snapdragon 650 which the Redmi Note 3 had. Most newer phones, including ones that are more expensive than the Redmi Note 4 - the Lenovo P2, use the Snapdragon 625 too. It is that good.

Snapdragon 625 also supports newer features

Even if we remove the conversation about peak performance, Snapdragon 625 has support for some newer technologies and features which weren’t in the 650 for various reasons.

For instance, the Snapdragon 650 uses Adreno 506 graphics cores clocked at 650MHz while the Snapdragon 650 uses Adreno 510 cores clocked at 550MHz. The 100MHz boost may not visible to the naked eye and it may not matter much. However, the Adreno 506 supports OpenGL ES 3.1 while the Adreno 510 on the Snapdragon 650 doesn’t support this. This shows up in raw graphics performance games like Dead Trigger 2, Modern Combat and the likes as the games are optimised of the for the OpenGL ES 3.1 API. The performance boost is significant with faster loading times and no drops in frame rates.

Moreover, the Snapdragon 625 used in the Redmi Note 4 comes with a faster block of LTE modem; the X9 as compared to X8 LTE modem found in the Snapdragon 650. There is a performance boost in uplink speed as a result, provided the network supports.

In addition, the Snapdragon 625 comes with dual ISP support to the tune of high-resolution 24-megapixels. This was first introduced in the Snapdragon 820 and was then ported over to the mid-range Snapdragon 625 as well as the Snapdragon 650. Although the Snapdragon 650 can only support sensors up to 21-megapixels. This allows mid-range phones to come with high-resolution dual-cameras. This is again something of a superiority that the 625 has over the 650, but in the case of the Redmi Note 4 it doesn’t come into play. However, the ISP on the 625 could be one of the reasons that it has a wildly better camera than the Redmi Note 3 which used the 650.

The only place where the Snapdragon 650 is superior is the support for quadHD screens as opposed to Snapdragon 625 which can only support fullHD panels. But again in the case of a phone like the Redmi Note 4 this is a non-issue because it has a full HD 5.5-inch screen, so it doesn’t need the extra headroom that the 650 provides. Even the Redmi Note 3 didn’t leverage this feature as it also had a 1080p screen.

The Snapdragon 650 also comes with Qualcomm's Voice Activation technology that enables users to call up voice-assistants when the screen is locked. Again, this is something that’s bit of unused feature as these phones don’t have a true voice assistant, they only have Google Now, that too not in its entirety as Mi UI 8 doesn’t support Google Now on Tap.

On the Snapdragon 625, this feature is absent, however, it comes with HD noise cancellation technology so the audio in general sounds much better. This feature makes more sense in the context of the Redmi Note 4 which will will result in clearer calls.

Otherwise, both processor comes with mostly similar feature sets with support for 4K Ultra HD video recording at 30fps and playback using HEVC and AVC codecs. Both have support for Qualcomm's Quick Charge 3.0 as well as its security support.

As a result, the Redmi Note 4 that launched yesterday, even though may feel similar to the Redmi Note 3 that was Xiaomi's best-selling device of all time in India, the use of the 14nm Snapdragon 625 processor will make all the difference in the experience.