Luffy's Stupidity comes from his simple-minded nature and his go with the flow attitude. While he doesn't care what is happening around the world or with things that don't concern him. In battle he has shown his true intelligence with his Creativity and able to learn and understand concepts just by experience. Like with learn Soru by seeing it and understanding how it works, and by learning the basics of Haki in a year and a half.
While Naruto Stupidity comes off as him not knowing basic things. Like the Shadow Clone memory link, or even Basic Chakra Control, without any real explanation on why he don't know it. Even after Two Years with Jiraiya he came back basically at the level of a "Proper Gennin".
While Naruto Stupidity comes off as him not knowing basic things. Like the Shadow Clone memory link, or even Basic Chakra Control, without any real explanation on why he don't know it. Even after Two Years with Jiraiya he came back basically at the level of a "Proper Gennin".