Soy products are relatively inexpensive. Whey protein is obtained during the processing of milk to cheese. Whey is a complete protein. Exaggerated claims have been made that whey is the best source of protein by sellers of whey protein supplements. Although an excellent protein source whey is not better than meats or dairy products.
Whey protein is generally more expensive than soy based protein.
Soy and whey are the most common constituents of infant formulas. In fact, infant formulas and protein powder supplements have many things in common. The overall quality of infant formula is more consistent and uniform than supplement powders. One will frequently find advertisements touting individual amino acids as being the key to greater strength, size or stamina. There is no evidence that high intake of any single amino acid helps with anything.