Did someone really ask this question? Really. FWIW, they were both wrong. The labor theory of value is false. Subjective value is true and marginalism has overwhelmingly demonstrated so.
Smith went to his grave thinking he was right, and he was right on the absurdly irreplacable returns of cooperation. But he was wrong on the labor theory of value.
Marx went to his grave knowing he was wrong. He read the marginalists and stopped writing. But he couldn’t stop taking income from Engels, so he pretended that he kept working.
Nothing more came from Marx – because his entire premise was wrong, and history has been unkind to his legacy.