If I'm not ordering my protein and supplements from VitaCost, I'm getting it from Vitamin Shoppe. Their prices are low, and they price match. The selections are good, and the workers there know where everything is at and are more than willing to help you if you need to find something.
They also have their own brands which is comparable to some name brands out there. As long as you do your homework with knowing the ingredients and potency you're looking for- you can always opt for their brands. The only Vitamin Shoppe branded item I've gotten is their Psyillium Husks. Good to know they have more options, but I wish they'd carry more Stevia choices.
As far as a supplement shops go, I'll choose them over GNC.