Your analysis is right on the mark! Congratulations for understanding something that most people simply do not, even after it is explained to them.
Your understanding of this concept will save you a great deal of taxes over the course of your life.
Actually, the tax benefits are even greater than 10% in your case, and here are the reasons why...(this description is cut and pasted from an earlier discussion):
1) You get an immediate tax reduction equal to your marginal tax rate. If you are currently in your peak earning years, you are probably in a high marginal tax bracket, say 25% or higher, and you will save 25% or more of every dollar you invest in a tax deductible plan. Then, when you retire and begin withdrawing that money, you will pay taxes based on your lower AVERAGE tax rate (aka effective tax rate) in retirement,
not your marginal tax rate in retirement. Your average tax rate is almost always lower than your marginal tax rate. For example, a married couple in retirement can withdraw at least $19,000 from their tax deferred accounts TAX FREE because of the standard deduction and their combined personal exemptions. This number may be higher if they have higher deductions or additional tax credits. They could withdraw $19,000 from their tax deferred accounts completely tax free in any given year, and supplement this income with other tax free sources, such as regular savings (withdrawals from regular savings are tax free), or Roth accounts. Even if they withdraw more than 19k in my example, they would only be pushed into the 10% marginal tax rate for the next chunk of income. So they could withdraw say 30k, and pay approximately 1,100 in taxes on the total 30k, which is an effective tax rate of less than 4%! (Remember that they saved 25% of every dollar that they contributed while working, so that is a tax savings of 21%).
If you pay state income tax, your savings are even more dramatic. People who suggest that a Roth IRA and a 401k are a wash if you will be in the same tax bracket in retirement simply don't understand this.
2) Your fixed expenses in retirement may be lower than they are now (no mortgage, no tuition bills or other child related expenses, no car payments, no work related expenses). You will also no longer need to save a chunk of your income for retirement. Therefore, when you retire, you will likely be able to maintain the same standard of living on less income, which means you will be in a lower marginal tax bracket in retirement. If you want to live a more extravagant lifestyle and withdraw money into the higher tax brackets, so be it, you will have that choice. To that extent, and to that extent only, the Roth may prove to be a better choice in the future, but that does not prove that a Roth is better choice as the first option for your investment money now.
3) By contributing to tax deferred plans, you can reduce your current adjusted gross income (AGI) below the threshold at which you can fully take advantage of certain tax credits or tax deductions, such as the child tax credit, or the earned income credit, or the student loan interest deduction, or other credits. If you did not fully take advantage of tax deductible investment plans (and instead contribute to a Roth IRA), your AGI would be correspondingly higher, and you would lose some tax credits, or, the amount of certain tax credits would be reduced. By contrast, investing in a Roth does not lower your AGI.
4) While I agree with the consensus that tax rates will likely be higher in the future, I think it's somewhat naive to have faith that congress will never tax Roth withdrawals, no matter how desperate our government may be in the future for tax revenue. There is a lot of tinkering that can be done in the future, such as reducing the eligibility to take tax free withdrawals, limiting the amount of annual tax free withdrawals, etc. It can (and I think it will) happen.
5) You will retain the option of converting some of your tax deductible funds to a Roth IRA at lower marginal tax rates in the future. For example, you may decide to retire before you are eligible for social security benefits, and withdraw taxable savings to pay your expenses until social security begins. By doing this, you will be using "return of capital" which is not taxed as income, and you may find yourself in a very low tax bracket for a period of time, maybe even a zero tax bracket, and you can use up your lower tax brackets during that time period to convert tax deferred IRAs to a Roth IRA and pay tax on that money at your then lower tax rates. By contrast, funds contributed to a Roth IRA can never be converted to a traditional deductible IRA.
For a more detailed discussion and examples, get the Boglehead's Guide to Retirement Planning, and read chapter 10.
