Actually if naruto was in jiraiya exact situation, he would also lose with low difficulty the same way ms sasuke would.Thank you. You normally back the Uchiha don't you?(not being a d**k, just asking)
I posted this because I believe that even though Naruto did win this fight against Pain, I think there is more to it than just who is stronger. As I've said many times before,it's all about having the right moves to take someone out.
Sasuke, doesn't have the right moves/style or skills for Pain. Thus he loses.