In 699, Sasuke has an internal monologue about how he worked hard everyday and kept getting frustrated at Naruto's random growths. Which is 100% true.
Dude learned shadow clone jutsu in a few hours, rasengan in a week, can summon boss toads because he's too dumb to know better.
Sasuke left the village to get better training, Naruto didn't put any real training in until the rasenshuriken