almost all webcams max out at a 640x480 resolution, so as far as image quality, they will be almost the same. (i.e. all models from logitech and creative) The main differences will be the appearance of the unit, and the software package it comes with. If you could care less about its looks or the software bundle, just get a cheap logitech quickcam express or something like that... you can find one shipped for about 30$
If you are getting it to record video with, know that you will only be able to record full motion (30fps) video at lower resolutions (around 320x240 roughly).