"Choose Roth if you're young" is advice that's right often enough to survive, and wrong often enough to cost people real money. The actual answer depends on one comparison: your tax rate today versus your expected tax rate when you withdraw.
The mechanical difference, in one sentence each
Traditional IRA: you get a tax deduction now, contributions grow tax-deferred, and you pay ordinary income tax on withdrawals in retirement. Roth IRA: you contribute after-tax money now, it grows tax-free, and qualified withdrawals in retirement are completely tax-free — including all the growth.
The actual decision rule
If you expect your tax rate in retirement to be lower than your current rate, traditional generally wins — you take the deduction now while your rate is high, and pay tax later at a lower rate. If you expect your retirement tax rate to be higher or the same, Roth generally wins — you pay tax now at a known rate instead of an unknown, possibly higher, future rate.
Why "young people should pick Roth" is usually true but not always: most young earners are in a lower tax bracket than they'll be in later in their careers, which favors paying tax now (Roth) while the rate is low. But a young high earner already in a top bracket, or someone who expects a lower-spending retirement than their current lifestyle, can genuinely be better off with traditional — the rule of thumb assumes an income trajectory that doesn't apply to everyone.
Three factors that shift the math beyond your tax bracket
- Required Minimum Distributions (RMDs): traditional IRAs force withdrawals starting at age 73, whether you need the income or not, which can push you into a higher bracket or affect Medicare premiums. Roth IRAs have no RMDs during the original owner's lifetime.
- Estate planning: a Roth IRA passed to heirs is tax-free income to them, subject to a 10-year distribution window — often a meaningfully better inheritance than a traditional IRA, which heirs must pay ordinary income tax on as they withdraw.
- Income limits: Roth IRA contributions phase out at higher incomes; traditional IRA deductibility phases out if you're covered by a workplace plan and earn above certain thresholds. High earners sometimes lose the choice entirely and default to a "backdoor Roth" strategy instead.
The version nobody mentions: you don't have to pick just one
Splitting contributions between both account types — a strategy sometimes called tax diversification — hedges against not knowing your future tax rate with certainty. Having both traditional and Roth balances in retirement gives you flexibility to control your taxable income year to year by choosing which account to draw from.
This is general information, not personalized advice — a fee-only financial planner or CPA can run the specific numbers for your income trajectory and current bracket.