I was wonder what, other than cost, makes different phytoestrogen sources better/worse than each other. In particular, what's the difference between Pueraria Mirifica and herbs like fenugreek, etc. I'd imagine the potency levels are different, but can't that be overcome by just taking more/less of a herb depending on potency?
There is actually no such thing as phytoestrogen - what you are referring to are a group of substances known as phytoestrogens (in the plural). There are different classes of phytoestrogens, so one source of phytoestrogens may be quite different to another. However, your point about potency is still valid, because where phytoestrogens are similar you can increase the potency of what you're taking simply by taking a higher amount of herbs.