A:Answer The Nikon D5500 uses an EXPEED image processor which provides sharply detailed images in low light up to 25,600 ISO and a 39 point AF system with 9 highly accurate cross-type sensors for enhanced AF accuracy. The Nikon D5600, which was released after the D5500, has a 39 point AF system and a top ISO of 25,600, which expands another 6,400 when used in Night Landscape mode. The biggest difference these two cameras have is the way in which they wirelessly transfer images to a compatible smart device ; the D5500 uses WiFi and connects by using the Wireless Mobile Utility (WMU) app while the D5600 uses Bluetooth and WiFi to connect with the SnapBridge application. Either one of these cameras would be a great choice to add to your growing camera bag.