The Microsoft Lumia 640 is more compact of the two with a 5" 720p screen and is will take on the Moto G (2015) at a Moto E (2015) price.
The one we handled had a glossy polycarbonate body and one of the brightest orange colors we've seen in person. These high-visibility colors are classic Lumia, Stephen Elop had the Cyan version in his hands, but there are also the more muted Black and White colors.
The Lumia 640 measures 8.8mm, pleasantly thin for this price range, but still carries the Lumia weight, 145g in this case.
The screen is still an IPS LCD with ClearBlack and Gorilla Glass protection, while the pixel density went up to just under 300ppi. The viewing angles and color rendering look great.
The camera department lost some of its headlining features, but is still much better than the current 6-series and below.
The main camera is an 8MP shooter that can record 1080p video - a big jump from the 5MP/720p of the Lumia 635. The Lumia 630 and below couldn't even do 720p and had no selfie camera. Anyway, the main camera uses a small 1/4" BSI sensor with a 28mmm f/2.2 lens.
The Lumia 640 selfie camera is not as impressive as on the XL model, but it's still a 1MP/720p shooter. This phone also supports the Dynamic flash and Rich capture features like the 640 XL model.
The battery is smaller though still good for the size. 2,500mAh gets you over 17 hours of talking on a 3G network and nearly 11 hours of Wi-Fi web browsing.