in reality, you don't need a puppy food at all. a good quality product with the designation "for all lifestages" is fine. just make sure you do
not feed a food that just states "for maintenance" to a growing pup.
it's much better to let a puppy grow slowly and evenly, even if that means it will reach its mature size and weight a little later. overfeeding will cause them to grow at the maximum rate, which puts a lot of stress on the skeleton and can lead to other health problems as well.
for anyone who hasn't read it yet, here's a great article on a study done by the cornell university:
http://www.news.cornell.edu/Chronicle/02/12.12.02/dog-diet.html