I use a webcam. One of the minuses for it is if you have any LEDs on the X extruder carriage to light up your print area, they will often "wash out" the image so you can't see the print. There is no brightness setting for using a USB camera, as opposed to using the RPi camera. Another minus would be you'd have to come up with your own mounting solution if someone else hasn't designed one for your particular webcam, unlike the RPi camera, which has many mounts and cases designed for it already. A plus for the USB webcam is long cords, you can put it anywhere. So far all I've seen is a maximum of 24 inches for the RPi camera, which may limit its location options.