Fistful was only Leone's second film, so it's a bit unfair to even compare the two in terms of directorial quality. I don't know if anyone could say with a straight face that Fistful is better than Yojimbo, except if they're biased towards Western culture. I appreciate that Fistfull wasn't a direct ripoff, and changed quite a bit of the tone and characters, basically using Akira's film as a template (though both are apparently unlicensed adaptations of a book called Red Harvest).