The amount you "put in" is taxed either way. The only difference is when it is taxed. With a Roth, you're taxed only on the amount you "put in", immediately. With a traditional, you're taxed on both the amount you "put in" as well as any gains, but only after you withdraw it all.
With a traditional retirement account, you're taxed on both the money invested as well as the gains from that money. With a Roth retirement account, you're taxed only on the money invested, and not the gains. This, to me, makes a Roth retirement account considerably more attractive, particularly since after a long time of accruing reasonable yields, a majority of most retirement accounts' values stem from capital gains, not principal. Is it not true that in the long term, the value of a retirement account is dominated by capital gains, not principal?
Of course, I recognize that there's many variables here, so this may not be the case for everyone. For example, perhaps one somehow has a very high tax rate as a worker saving for retirement, and a very low tax rate as a retired person drawing from retirement accounts. In such a scenario, it might make more sense to pay the tax up-front and invest in a traditional retirement account, only paying (the lower rate) tax when drawing from these retirement accounts. However, since the bulk of most retirement accounts (at retirement) is from capital gains, not principal, I can't imagine a marginally lower tax rate compensating for a vastly larger sum of taxable income/gains in any ordinary situation. Another scenario is where the investor enjoys only miniscule gains. In this case, the retirement account would contain primarily principal, and the benefit of the Roth would likely be outweighed by the traditional account's (usually) better tax rates. However, I don't see either of these scenarios as especially likely. Am I missing some other (hopefully more likely) scenario where the traditional retirement account is preferable to a Roth?
I am not an accountant. Your mileage may vary. Side effects may include nausea, stroke, or death.