Compare Roth 401(k) and Traditional 401(k) to see which gives you more after-tax retirement income.
Traditional: Contributions are pre-tax (reduce taxable income now), grow tax-deferred, taxed as income when withdrawn. Roth: Contributions are after-tax, grow tax-free, withdrawals are tax-free.
Choose Traditional if you expect a lower tax rate in retirement; choose Roth if you expect the same or higher.