A Roth 401(k) allows people to divert up to $17,000 annually (as of 2014) if they are under 50 and $22,500 if they are over 50, while a Roth IRA allows for $5,500 a year for those under 50 and $6,500 for those over. A Roth IRA may exist indefinitely and be passed down to the next generation, while you must start taking distributions for a Roth 401(k) beginning at age 70½.