Should I contribute to a Roth 401(k) or Traditional 401(k)?

If you expect higher taxes in retirement (young, early career, tax rates may rise), choose Roth — pay taxes now at a lower rate. If you're in your peak earning years and expect lower taxes in retirement, choose Traditional for the tax deduction now. Many advisors recommend splitting contributions 50/50 for tax diversification, since nobody can predict future tax rates with certainty.