The Silverpuppy base model for $140 is all you really need to make high quality CS. I like the addition of the magnetic stirrer but it's an extra $50 and if you are on a budget not really necessary. The Silveredge does not have polarity swapping electrodes, auto shutoff, or current control as far as I know. The current control helps you get the smallest silver particle size. Polarity swapping electrodes prevent oxide buildup on the electrodes. Auto mode shuts off at something like 15ppm so you can turn it on and have it turn off by itself when your CS is ready. Manual mode allows you to make as high ppm as you want perhaps up to 30-40ppm. You won't find these features on many other units. Besides the Silvergen this unit is recommended as well by Silverpuppy so it should perform well http://www.wishgranted.com/Colloidal-Silver-Generator--Colloidal-Silver-Water...