Nutro, and all the others you have mentioned in your original post are premium quality foods.
If that is the diet you wish to stick with, then like Di, I would ask what is wrong with what you are feeding at present? As in, what is the reason you are considering changing?
Some owners find their dogs have too loose stools on a certain brand, or copious amounts of crap, or dry and itchy skin, or ear infections...the list goes on. Most ppl will change a food/diet whenthey feel a problem is occurring in the well-being of their dog, and the obvious culprit is the food.
If you are not having any trouble, why change, if you are happy with it, and your dog?
I've heard great stuff about Nutro, also Royal Canin is top quality for a dry food, and I;ve heard excellent reports about Innova, but each dog is different.