The DBK21 04.AS leaves the 900nc for dead and the reason is because the DBK21 04.AS is a true usb 2 device and can move way more data. The 900nc can reach great FPS though to do so you need to use compression aka a lossy codec, this means your images are all crappy and stacking isnt going to do a thing. With a lossless codec (what you need) the 900nc is best about 10-15fps witch is ok with great seeing. The DBK21 04.AS can pull way higher fps due to its real usb 2 interface with a lossless codec so you can pull 60fps and get those A1 frames in avg seeing condition. The flea3 usb 3.0 can pull 150 fps with its usb 3 interface so i help that gives you and idea of why there priced that way
