<prompt> Human: Paying taxes NOW instead of at retirement is optimal? Because tax rates are so low, and most likely much higher in future?Through the taxed now Roth, for tax free growth no taxes later.  <response>: You want mix though, because you will still have the standard deduction on retirement. You want to fill up all your tax free space with pre tax retirement savings, so you get the gains earned on money you otherwise would have spent on taxes, and you keep the tax money, and all tax free to to currently 12k a person. You wouldnt want to waste Roth income on you tax free space each year. 