Roth: "Money grows tax-deferredd and is tax-free when distributed, as long as certain criteria are met."
Pros: You can withdraw from the Roth anything you put into it whenever you want, no penalties, no taxes, no questions other than filling out a form. It's not much more involved than taking money from your checking account. That's the contribution part. Anything you earn above what you contribute is still subject to early withdrawal penalties and such, but is totally tax free. Not tax deferred.
What's the downside? Mostly the fact that when you do the conversion you will pay all the tax up front. The IRS is still getting paid, that's why they don't care if you withdraw it later.
Purely financially the Roth vs. traditional question is more or less a tossup. I like having a Roth simply because it means I don't have to consider it as "locked-up" money. Instead of diverting funds to a taxable savings account I just stuff as much as possible to a Roth. I can get it back with no fuss or penalty in an emergency, and in the meantime get tax-free returns. That beats a savings account any day.