While Microsoft’s high-end phones face fierce competition from the other big companies, the low-end market is where they hold bragging rights. Their very affordable phones in the 500 series and 600 series have made it possible for people to buy devices from a well-known vendor other than the QMobiles and other Chinese manufacturers. The 640 is a bigger step, though, as Microsoft attempt to squeeze into the mid-range market as well, with an LTE and Dual-SIM option.
The 640, along with its big brother XL, have really good displays in IPS LCDs of 5.0 and 5.7 inches respectively at 720 x 1280 resolution. This means lesser pixel density for the XL but it still is pretty good for a mid-range device. Both phones have a Corning Gorilla Glass 3 protection, and the option for Dual-SIM or LTE or both.
Both phones come with Windows Phone 8.1 with Lumia Denim out of the box, powered by Qualcomm Snapdragon 400 chipset that allows for a quad-core 1.2 GHz Cortex-A7 processor accompanied by 1 GB of RAM. Adreno 305 graphics on both the devices promises good performance in several applications across the Windows Marketplace. It comes with 8GB internal memory and is expandable up to 128 GB via microSD slot. All in all, both phones have pretty good hardware for a Windows Phone.
When you read Carl Zeiss optics on the back, you know the camera is going to perform really well. The Lumia 640 has an 8 megapixels camera on the rear with a very respectable aperture that will perform well outdoors in daylight and in some low-light conditions. The XL, however, has a 13 megapixels camera with a wider aperture that will surely perform well even in low light situations. The front on the 640 is only 1 megapixel compared to the 5 megapixels on the XL.
Both phones have removable batteries which is always a plus for the mid-range market who often want to be able to replace batteries after a while, and in terms of amperage the numbers are pretty respectable. The 640 has a 2500 mAh battery whereas the XL has a 3000 mAh battery and both will get you about 2 days of use on average.