Using 2017 tax rates, note that if you are at the $18,000 end of the income range specified, can make an IRA contribution of at least about $1,525 and qualify for the Retirement Savings Contributions Credit, there is a good chance that there would be NO tax benefit to a traditional IRA contribution over a Roth IRA contribution. The Retirement Savings Contributions Credit that you would get for this contribution to either a traditional IRA or a Roth IRA would make the deduction for a traditional IRA contribution worthless with respect to your federal income taxes.
However, don't forget to consider state income taxes. The deduction for a traditional IRA contribution might reduce state income taxes where a Roth IRA contribution would not.
