I've never heard of Nutro Source. Nutro has Nutro Max, Nutro Natural Choice, and Nutro Ultra. Of the three, only the Ultra is any good. It's still very grain heavy and I personally wouldn't feed it, but it's not terrible.
Take note though: Nutro has been purchased by Purina. The "Natural Choice" line has been in the repackaging phase for several months now and is for the most part available only on a limited basis. I don't know if they're being reformulated as well as repackaged.