I keep seeing people mention Rin's death and how it shaped Obito, and I think this is where everyone in this thread is missing the real point where Naruto and Obito differ.
Maturity is learning from your experiences as you grow up and become older. Rin's death is not the key point here -- it's the fact that Obito's set of beliefs were spoon-fed to him that makes him truly immature. He did not even try to understand the situation, he did not search for answers, he did not try to learn the truth from Kakashi. Instead he retreated to Madara's cave and without thinking things through on his own, readily accepted whatever crap Madara was willing to feed him.
Naruto, on the other hand, is willing to look for an answer on his own, and grow from his own experiences. No matter how slow this process is, he's willing to go through it. Obito was not; instead he ran straight back to Madara, unwilling to find out the truth for himself. This is, ultimately, what makes the difference between the two of them.