Look at digital cameras. A free cellphone can have 25Megapixels and take so so pictures. Or you can get a fancy Nikon digital SLR that is only 8 megapixels with a $4000 lense and take amazing national geographic quality pictures.
When it comes to imaging it's all about the lense, the auto focus, the lighting, white balance, etc.... If you want a good webcam go with Logitech, they are the best. Microsoft makes a good value one, but the logitechs are better at a higher price point.