Should I contribute to a Traditional IRA or a Roth IRA?

From FinancialPlanning

Just like Roth conversions, this topic has been debated many times on MIFP. The missing piece of information is future tax rates -- both what they'll be, and which ones will apply to you specifically (based on your wealth and income many years in the future).

Generally speaking, if your income tax bracket is low, you should put money in a Roth IRA. You aren't giving up much of a tax benefit today, and all of your future earnings will be tax-free.

If your future tax bracket is likely to be low, and it's high today, you're more likely to benefit from a Traditional IRA with its immediate tax deduction.

Unfortunately most people can't say with much certainty that either of these cases apply to them, and it gets down to the appeal of "no future tax" (Roth) vs. "tax deduction today" (Trad-IRA).

For some people the decision is simplified because of contribution & deduction rules. For example if you contribute to a 401(k) plan at work, your contribution to a Traditional IRA will probably be nondeductible. If so, and you qualify for a Roth, you might as well make your IRA contribution there (where earnings will be tax-free) instead of to a nondeductible IRA (where future earnings will be taxed at withdrawal).