[Help] Anyone try Kirkland Dog foods?

I am bringing home my adopted Chihuahua mix in two weeks and am planing on changing his food from Purina (which makes his poops awful) to one of the Costco Kirkland brand food (which is what my parents' dog is on). They have several different types in store where I live, but no small dog specific ones.

Anyone have any experience with the regular Kirkland brand or the Kirkland Nature's Domain? Even if it is just how your dog likes it. They are a reasonable price for a big bag and the ND is grain free, but I would like to know the pros and cons of it before I commit to a big bag.