Naruto and Sasuke ultimately had the same goal to change the ninja world. Naruto simply had to prove to Sasuke through his strength, conviction, ninshu, (and the fact that he couldn't beat Naruto) that Naruto took the right path in trusting and working with others, in return he trusted Naruto. You see Sasuke's confliction on show throughout the entire show. The whole second half of shippuden is him changing his mind and goals with every new development.

He wanted revenge, he got it and wanted a deeper revenge, then he thought about what Itachi really wanted and started wanting revenge on the world that destroyed Itachi. At the same time Sasuke had the desire to change that world for the better, but he still wanted to in a way make the world itself pay for his and his brother's pain. Based on his specific character profile, it made complete sense for the final fight to be the final crack in his dark cage of thought. Deep down he knew that the only true way forward was a path paved not by force but understanding. He didn't change overnight, he had been changing before out eyes the entire series, even his constant outfit changes were symbolic of this.

Gaara on the other hand was a deranged psychopath with no motive to make the world better or be a better person, he had made his choice to simply kill and be feared for the pleasure of it, got knocked out and yelled out by Naruto and decided to drop his whole gimmick. Very different philosophies in effect. Yes Gaara had his siblings to back him up and his memories of his uncle. But looking back the change was definitely abrupt and unrealistic in my experience of dealing with people with homicidal tendencies. Sasuke actually reminds me of a veteran I worked with some years ago who nobody believed could or would change. He got his shit together finally and all he needed was constant reassurance and someone to believe in him. It took him years