A traditional IRA is tax free going in, but taxed coming out. A Roth is the opposite and taxed going in, but tax free coming out.
Mathematically, they're equivalent. The only reason to choose one over the other is your personal income tax rate. If you think you'll pay a lower tax rate in retirement (because you won't be making as much, and thus will be in a lower tax bracket), then you'd pick a standard IRA. If you have a shit job now and expect to make more later, a Roth would make more sense.