Naruto would gain more confidence in his abilities at a faster rate. Since Hiruzen is an experienced and powerful ninja, his training methods would be more efficient. Naruto would start to believe in himself more quickly, which would in turn make him more assertive in his actions. He would also be more open to learning from others, as Hiruzen would instill in him the importance of continuous learning.
His understanding of the village and its values would deepen. Hiruzen could tell Naruto stories about the founding of the village and the sacrifices made. This would make Naruto more committed to protecting the village. He would also become more respected by the villagers earlier as they'd see the Hokage taking a personal interest in his training. Also, Naruto might develop a more refined sense of humor, as Hiruzen has a different kind of wisdom compared to his other mentors.
Naruto would become more well - rounded. With Hiruzen's training, he'd gain more discipline. In the original, Naruto was a bit of a wild card. But under Hiruzen, he'd learn to control his impulses better. For example, in battles, he'd think more strategically instead of just charging in.