I purchase my protein (and carbs) from the Protein Factory and Protein Customizer for one major reason: egg protein.
I am really sick of seeing all the big name companies flat-out rape people with their egg protein prices. It is not easy to find, and when I did, it was $10-$15 per pound. I get it for 4 bux a pound through Proteincustomizer.
If all you drink is whey, than the savings might not be THAT great compared to Optimum, but if you want anything else, get it from the Protein Factory or the Protein Customizer and tell the other companies that their days of fucking everyone are over.