Which is the best smartphone among Microsoft Lumia 640 vs Microsoft Lumia 540?

Well, it clearly depends on individual preferences to zero in on a smartphone. However, a brief comparative analysis may be helpful -
Design
Design wise both Lumia 540 and 640 appear similar. The 640 measures 141.3mm x 72.2mm x 8.8mm, while 540's physical dimensions are 140.2mm x 72.4mm x 8.8mm. The former weighs 146 grams and the latter is 145 grams. One will not find much of a difference here.

Display
Both the phones have 5 inch IPS LCD display. However, there is a difference in resolution - 640 has a HD resolution of 1280x720 while 540 has 960x540. The pixel density is 294 ppi and 220 ppi respectively. The 640 gains an upper hand here.

Camera
The Lumia 640 sports a 8 MP autofocus rear camera with LED flash and HD video recording capability. The front camera on 640 is 1MP. The 540 carries a 8 MP rear camera with almost same features but it has no HD video recording. It also lacks advanced camera features. However, the 540 carries a 5 MP front camera.

Hardware
The Microsoft Lumia 640 is powered by 1.2GHz Snapdragon 400 quad-core processor and Adreno 305 GPU. The 540 has a 1.2 GHz quad core Snapdragon 200 processor and Adreno 302 GPU. Performance Wise both the devices do not show any lag. Both the devices have 1 GB RAM and 8 GB internal memory expandable upto 128 GB . So, both of them look similar in this section.

Other features
The Microsoft Lumia 640 has a better battery at 3000 mAh while the 540 carries a capacity of 2200 mAh.

Price
Lumia 640 is priced at Rs. 9999 and the Lumia 540 is available at Rs. 10999.

Microsft Lumia 640 and Microsoft Lumia 540 are very fine products if you want to have a windows phone. Both comes with a very close price tag to each other. So, as you asked for a detailed comparison between these two smartphones, I would love to help you!

Display: There is nothing any 'to spot' difference between their display features. Both features 5 inches of screen and 720x1280 pixels of screen resolution.
Winner: Its a tie here!

Hardware: They both are really very close to each other in hardware specifications. Lumia 640 as well as Lumia 540, both have same RAM and internal memory, i.e., 1GB of RAM and 8GB of internal memory. But the difference arises in the processor as Lumia 540 has 1.2GHz quad-core Qualcomm Snapdragon 200 but Lumia 640 features a little bit higher processor - 1.2GHz quad-core Qualcomm Snapdragon 400.
Winner: Microsoft Lumia 640 wins due to its greater processor!

Camera: Again, there's nothing difference in their rear camera specs but the plus point for Lumia 540 arises in front camera specs. Lumia 540 has a 5 MP of front cam but Lumia 640 has a very poor front cam of 0.9 MP only.
Winner: Here, Microsoft Lumia 540 wins clearly!

Battery Life: Microsoft Lumia 540 has only 2200 mAh battery capacity whereas Lumia 640 features a much bigger battery of 2500 mAh.
Winner: Again, Microsoft 640 wins!

Gaming Experience: To have a much better gaming experience, you should go with Microsoft Lumia 640 as it has a greater processor. And it also supports Java which Lumia 540 lacks in!
Winner: Microsoft Lumia 640 is winner.

Here you can get the best comparison between Microsoft Lumia 640 and Microsoft Lumia 540. Keep reading to know the best one among those two.

Microsoft Lumia 640 vs Microsoft Lumia 540

General
Microsoft Lumia 640 measures its physical dimensions around 141.30 x 72.20 x 8.80 mm. The device weighs around 145 grams. Lumia 640 is powered by a powerful 2500 mAh battery. It is touchscreen device which has been recently released in February, 2015.

On the other end Microsoft Lumia 540's physical dimensions are 144.00 x 73.69 x 9.37 mm and weighs around 152 grams. It is also a touchscreen smartphone which is powered by removable battery of 2200 mAh.
Winner:- Microsoft Lumia 640 (Less weight, Slimmer, Good battery & Better design).

Display
Microsoft Lumia 640 sports a 5.00 inches IPS LCD display which supports 720p HD resolution. It has 294 PPI pixel density.

Whereas Lumia 540 also comes with the same IPS LCD 5.00 inches display which supports the resolutions of 720 x 1280 pixels. It has also has 294 PPI pixel density.
Winner:- Its a tie here.

Hardware
Microsoft Lumia 640 is powered with Qualcomm Snapdragon 400, 1.2GHz quad-core processor paired with 1 GB of RAM. The internal storage space of the device is 8 GB and the space can be extended using microSD card of upto 128 GB.

Whereas Microsoft Lumia 540 Qualcomm Snapdragon 200, 1.2GHz quad-core processor and is also paired with 1 GB of RAM. The internal storage space of this smartphone is 8 GB and the space can be extended using microSD card of upto 128 GB.
Winner:- Microsoft Lumia 640 (Better processor).

Camera
Microsoft Lumia 640 features a rear camera of 8 MP with flash and a front camera of just 0.9 MP.

Whereas Lumia 540 comes with a rear camera of 8 MP with flash and a front camera of 5 MP.
Winner:- Microsoft Lumia 540 (Better front camera).

Software
Microsoft Lumia 640 runs on Windows Phone 8.1. It also supports Java. Whereas Microsoft Lumia 540 also runs on Windows Phone 8.1 but it doesn't supports Java.
Winner:- Microsoft Lumia 640 (Java support)

Connectivity
Microsoft Lumia 640 supports Wi-Fi 802.11 b/ g/ n, GPS, Bluetooth, 3.55 mm audio jack, microUSB, Dual-SIM and it can also be charged via microUSB.

All those features are also present in Microsoft Lumia 540 except GPS.
Winner:- Microsoft Lumia 640 (GPS).

Sensors
Microsoft Lumia 640 comes packed with some sensors which are Compass/ Magnetometer, Proximity sensor, Accelerometer and Ambient light sensor. The same features are present in Microsoft Lumia 540.
Winner:- Its a tie here

Verdict
You can check the clear cut fight now. Most of the times the winner was Microsoft Lumia 640. So, according to me Lumia 640 would be a great buy.

Specs comparison between Microsoft Lumia 640 and Microsoft Lumia 540 :

OS : Both Lumia 540 and Lumia 640 operates on the Microsoft Windows Phone 8.1 OS.

Display : Both smartphones have IPS LCD capacitive touchscreen of 5 inches with a resolution of 720 x 1280 pixels and ClearBlack technology.

Memory : Both smartphones have 8 GB internal memory, 128 GB expandable memory and 1 GB RAM.

Camera : Lumia 640 has 8 MP rear camera and 1 MP front camera while Lumia 540 has 8 MP rear camera and 5 MP front camera.

Connectivity : Both Lumia 640 and 540 support Wi-Fi, Bluetooth v4.0, GPS, microUSB v2.0 connectivity.

Java : Java isn't supported in any of them.

Battery : Lumia 640 has Li-Ion 2500 mAh battery whereas Lumia 540 has Li-Ion 2200 mAh battery.