The Avast Premium is a product in its own right, Ultimate includes avast Premium and a number of other independent avast programs collated into the Avast Ultimate product.
So it would entirely depend on your needs as to which of these additional programs in the Ultimate product you need and would it be better/cheaper to have avast Premium and any other products. Bundling using the Ultimate product could be less expensive than choosing a couple, paying as individual products.
So you really need to look at the link given by Asyn to compare the product to your needs.
