ppm w/Silver Puppy? Yellow silver?

I have been trying to decide on a silver generator for some time, and I really want to make my final decision.
Here is my question: I am leaning towards Silver Puppy over Silver Gen since it seems to be more popular here, but it seems that it only makes 20ppm where you can choose different ppm with SilverGen. I know that 20ppm is considered to be good but why not make lower ppm and drink more of it? Wouldn't that be a better alternative since lower seems safer (I even heard some say not to go over 10ppm), and 20ppm really is as high as one should go (so why would I want to be at the upper limit if I can go lower and drink more and have the same effect)?

Also, what is the deal with the yellow silver. Some mentioned that puppy can make it yellow sometimes, which I am confused about because at elixa.com they say choose a generatot that CAN make yellow silver, where most say yellow isn't good. So should I or shouldn't I drink yellow silver?

Thank you.