Using both deuterium and tritium in nuclear fusion bombs is preferred because this combination releases significantly more energy compared to using only deuterium. The fusion of deuterium and tritium is also easier to achieve than the fusion of deuterium with itself. This increased energy output and efficiency make the deuterium-tritium reaction a powerful choice for nuclear weapons. The discussion highlights the advantages of this combination in terms of energy production and fusion feasibility. Overall, deuterium and tritium together create a more effective nuclear fusion reaction.