Unfortunately, the answer to this question “depends…”  If you are depositing pre-tax money into a retirement plan that affords tax deferred saving you will have to pay the IRS when those monies are withdrawn.  If your tax rate is significantly higher during retirement than when you were saving for retirement you could potentially be worse off from an after tax perspective than if you saved with after tax money while your tax rate was lower.  The opposite effect occurs if your tax rate is lower during retirement.  Many people consider doing some of both to mitigate this unknown risk and take advantage of the traditional and Roth IRAs for this purpose.