From that perspective, all formulas will meet your baby's nutritional needs. It could be that the source of protein is causing the price differential. As long as the nutritional requirements are met, the companies have the freedom to change the ingredients they use in their formulas. Ingredients can be a big factor in formula cost. According to the tables in the text published by the American Academy of Pediatrics, the major protein source in Enfamil and Similac is casein.
Carnation uses mainly whey protein.
The source of protein will not affect the nutritional content of the formula. Watch this report about showing affection to boys. Find out here. You should not rely on this information as a substitute for personal medical attention, diagnosis or hands-on treatment. If you are concerned about your health or that of a child's, please consult your family's health care provider immediately and do not wait for a response from our professionals.