The power scaling gap between Dragon Ball and One Piece is orders of magnitude too vast.
Luffy in Gear 5 is a monster within the One Piece universe โ reality-warping Toon Force, continental-level attacks, and Conqueror's Haki that can knock out armies. But the One Piece power scale simply doesn't approach Dragon Ball's.
Goku was destroying planets in early Dragon Ball Z. By Super, he's threatening universal destruction with stray punches. The gap between 'can split an island' (Luffy's approximate ceiling) and 'can destroy a universe' (Goku's baseline) is incomprehensible.
Luffy's rubber body wouldn't help โ Goku's ki attacks aren't blunt force, they're energy that vaporizes matter. Gear 5's cartoon physics are creative and unpredictable, but they haven't demonstrated resistance to universal-level force.
Goku's base power exceeds Luffy's peak by orders of magnitude. A casual ki blast from Goku would obliterate anything in One Piece. Ultra Instinct makes Goku impossible to hit regardless of Luffy's unpredictability.
Gear 5's Toon Force is genuinely wild and could create unexpected interactions with ki energy. Luffy's Conqueror's Haki bypasses physical defense. His rubber body absorbs blunt force. But the power gap is simply too extreme for any of this to matter.
Goku wins overwhelmingly. Luffy is one of anime's greatest protagonists and incredibly powerful in his own universe, but the power scaling gap between One Piece and Dragon Ball is too vast. This is a universe-buster vs. an island-buster.
Goku also fights
Monkey D. Luffy also fights