At such a young age a change is a change, whether it is from one formula of Purina to another or from the prescription Purina to a different brand. Whatever you decide transition slowly, gradually increasing the amount of new food while decreasing the old food over the course of at least a few days.
Given the choice between the three foods you mentioned I, personally, would choose Acana. Make sure if you do pick Acana that the formula you choose has an acceptable level of Calcium for a large breed puppy, because not all of the Acana formulas do. Also keep in mind, regardless of what brand you choose, that over feeding can and will cause loose stools and the recommended feeding amounts listed on the bags are usually quite generous.
Good luck with you new puppy!