What is the difference between before tax contribution and Roth 401k in terms of retirement savings?

The main difference between before-tax contributions and Roth 401(k) contributions is when you pay taxes on the money. Before-tax contributions are made with pre-tax dollars, meaning you pay taxes on the money when you withdraw it in retirement. Roth 401(k) contributions are made with after-tax dollars, so you pay taxes on the money before you contribute, and then you can withdraw it tax-free in retirement.