That depends on the range of the duel. In a close quarter area the M1Garand would win cuz of the higher firerate since its semi atomatic and the kar98 is bolt action (You have to manually rechamber after each shot) But since the kar98 was often used as an marksman rifle with a telescopic sight attached it would be much more precice at range.
But I would say overall, the M1 Garand would win cuz of its larger overall usability.
In a zombie apocalypse, who would "win" (survive longest) of Battlefield players or Call of Duty players?