The price of the Dymatize whey protein powder and the Nature's Life soy protein powder are about the same per pound on Amazon. The Dymatize product contains a little more protein per gram than the Nature's life product, so the Dymatize product is a little cheaper.
If you look at the Dymatize label, I think you will see that whey protein concentrate is the second listed ingredient, so you are not getting pure whey protein isolate. See my previous cite for the difference between isolate and concentrate.
I don't find your second cite at all credible. The authors, Sally Fallon & Mary G. Enig, are the cofounders of the Weston A. Price Foundation. First of all, this foundation is funded by the meat industry. Second of all, if you look at the foundation's website, you will see that they advocate eating a lot of beef and dairy products, including milk and butter.
I'm sorry, but I am not interested in advice from nutritionists who advocate consuming a lot of beef, milk, and butter. If you look at the website, you will see a lot of articles trashing soy products, and extolling the virtues of a diet high in saturated animal fats.
Here are a couple of articles about the Weston A. Price Foundation --
http://www.vegsource.com/news/2009/11/reflections-on-the-weston-a-price-foundation.html
http://www.vegsource.com/news/2010/07/the-truth-about-the-weston-price-foundation.html
I found this quote from the first cite telling --
"I regret to say that those running the Weston A. Price Foundation today seem to have their own agenda. They are proponents of the philosophy that in order to be healthy, people must eat large amounts of saturated fat from animal products. They insist that only with the regular consumption of lard, butter and other full-fat dairy products, and beef, can people derive the nutrients they need to be healthy.
Toward that end, the Foundation has widely publicized an article written by a former member of the Foundation's Board of Directors, Stephen Byrnes, titled "The Myths of Vegetarianism."
The article is harshly critical of vegetarian diets, and concludes with an "About the Author" section which states: "Stephen Byrnes... enjoys robust health on a diet that includes butter, cream, eggs, meat, whole milk, dairy products and offal." In fact, Stephen Byrnes suffered a fatal stroke in June, 2004. According to reports of his death, he had yet to reach his 40th birthday.
Here is the Wikipedia article on the Weston A. Price Foundation --
http://en.wikipedia.org/wiki/Weston_A._Price_Foundation
Here is a very detailed rebuttal of the Fallon and Enig article you cited --
http://www.johnrobbins.info/what-about-soy/
Soy protein is a high quality protein, and it is the most complete plant-based protein, as far as I know. As pointed out in the cite in my first comment, soy protein contains much higher levels of two key amino acids than whey protein -- glutamine and ornithine.
Besides soy protein powder, I also use soy-based lecithin, soy milk, and soy-based veggieburgers. It's pretty tough to get enough protein on a vegetarian diet without soy. I do eat cheese and eggs, but I wish I could quit cheese. It's just so yummy. I have tried soy-based cheese, and it's not an acceptable substitute.
I suggest you do some more research on the subject. Don't base your decision on information from "nutritionists" who advocate consuming large amounts of saturated animal fat. It seems obvious to me that soy milk is preferable to cow's milk, and that Smart Balance is preferable to butter.
William Coleman (ramashiva)