401k in general is the best:
- employer match
- authomatic contribution - convinuence
- reduces your AGI - affect other deductions (EIC, child tax credit, educational credits, etc)
- Additional saver's Tax Credit
- in case of emergency - the loan may be taken
Roth IRA - very good additional to 401K
- no required distribution
- earning will not be taxable
- diversification of investment
Trad IRA - if no 401K plan at work:
- all benefits of 401K except employer's match