I was feeding my dog "Principle" and was running low so purchased a 4kg bag of Optimum $14 approx. emptied it into my food bin with some principle still in the bin and I couldnt tell the difference, same shape ..colour etc. I spend $62 for a 20kg bag of Principle.
But hey the Optimum bag is shiney!!! jk
My boy loves Principle or the Optimum as it happens. He also gets fresh roo meat, a chicken carcas every other day and a spoon of yoghurt (cos he loves it).
He is happy healthy and so are his "poooos" :D :D
I have also fed him Eukanuba, Hills, Advanced.
Just my experience
love n drools
Caz n Odin