How does Authority large breed puppy compare to BLUE large breed puppy?

I know BLUE is the better of the two, that is what we are currently feeding our Mastiffs. But my husband was laid off recently, and the Authority seems much more affordable at the moment. The cashier at PetSmart said it is not as good, but better than a lot of the other kibbles out there (she named Pro Plan off the top of her head) Would I be doing my dogs a huge disgrace by temporarily switching to this kibble? We are very satisfied with BLUE, it's just getting to be pricey with no job & 3 kids. Not to mention we are feeding two mastiffs, we're buying 2 - 30lbs. bags a month.