Purina puppy chow vs. Royal Canin?

We have a 4 month old shih-tzu/poodle mix. We had been feeding her Royal Canin mini puppy 33 from Petco at $14 for 11 cups but were shocked when we were in the grocery store and saw Purina puppy chow for $5 for 4.4 lbs. We bought it and she likes it just as much... I'm just wondering if anyone knows if there is much nutritional difference between the two, and if so, is it worth the 10 extra dollars.