Traditional, Roth or ETF

This January I'm going to set up a retirement plan that my wife will contribute to. Currently, she has no retirement plan in place as her employer doesn't offer one. I have a few things in mind: the traditional IRA, the Roth IRA or an ETF like Nasdaq's QQQ or the S&P's Spiders. I know the tax benefits of the Roth vs. the traditional IRA, but I've also been researching investing in ETF's as well as they seem to be growing in popularity. I'm all over the place with these and can't make up my mind as to which one to go with. It'll probably come down to personal preference. Check back and see in a month or two to see what we come up with.