Well, I agree that we can see a paralell between Naruto's and Sasuke's developments.
Sasuke gambled his life to obtain new powers, as a shortcurt to reach his goals. What goal? Revenge, selfish revenge.
On the other hand, take Naruto. He wants to protect his friends, his village, to make the system better for everyone and especially for those who like him was alone. That's his leitmotiv: fight for others (I didn't say LOVE , there's a big difference I think). That's why he put and will put so muche effort into this: Kage Bunshins training is really impressive and effective. But take a look, compared to attacking a severed wounded Oro or gaining by luck (or Itachi's will) MS, it takes time, effort, stress. He uses a huge amount of chakra, needs to be careful Kyubi won't take over him. When he releases all Bunshins, yes he gains all their memories, but I remember that the strain and the stress is so hard that it's a direct KO and black out. Who would train like this and experience such horrible pain twice? He'll gladly do it, if it's for others.
Sasuke did put himself to extreme battles and strain, but it was to survive, to reach his selfish goals. He represents him as an avenger, but all his previous "truth" was blown away by Madara... and what will he do? Revengeful strike again.
Sasuke's development is recquired to emphasize Naruto's character and will.