With your retirement accounts, if you can max them out or come close, you should go with a ROTH account.
The reason for this is simple: $15,000 after tax dollars is more than $15,000 pre-tax dollars (ditto for $4000 after tax dollars vs. $4000 pre-tax dollars).
Assuming the money is going to double & 10% taxes (for simplicity):
Post Taxed: ($15,000 * 2) * .9 = $27,000
Pre Taxed: ($15,000 *.9) * 2 = $27,000
In terms of after tax value put in:
Traditional: $15,000 * .9 = $13,500 after tax contribution
ROTH: ($16,666 * .9) = $15,000 after tax contribution
The more you make, the greater the difference is. Someone maxing out contributions in the 10% bracket only takes a 10% hit by going with a traditional program over a ROTH. Someone in the 38.6% bracket looses more than 1/3 of the potential value by contributing to a traditional IRA vs a Roth.
In the case of an IRA, you can only contribute to a ROTH account up to a certain level of income. In the case of a 401(k), you can only contribute to a ROTH account if your company offers it, but there is no income limit.
High income earners, welcome back to ROTH territory.
401(k)s - IRS, Investopedia
ROTH 401(k) - IRS, Roth401k.com, Smartmoney
IRAs - IRS, Investopedia
ROTH IRAs - IRS, Rothira.com, Investopedia