What’s the difference between the two? Well, according to Xdkb.net, the Desire 516 has dual SIM capabilities, while the 316 doesn’t. This means that the handsets share the same design (seen above), as well as most of their features. As previously reported, the new Desire is far from being a high-end device. It sports a 5-inch qHD (540 x 960) display, runs Android Jelly Bean, and offers a 5MP rear camera.
There will be a Desire 516t model that features 512MB of RAM and a quad-core 1.3GHz processor (probably made by MediaTek), while a Desire 516w should come with 1GB of RAM and a quad-core 1.2GHz CPU - possibly a Qualcomm Snapdragon. The 516w might be made for international markets. However, nothing’s confirmed at this point.
source: Xdkb.net (translated)