Both have annual contribution limits: 401k = $18,000/year including employer match, Roth = $5,500/year
Both have catch up provisions if you are over 50 years of age
401(k) is tax deferred but a Roth is with after tax contributions, grows tax free and distributions are tax free.
Roths have income limits as well:
If married filing jointly and make over $181,001 annual income, ineligible for Roth.
Single – Annual income greater than $120,000, ineligible for Roth.
Neither of them have any guarantee of returns and no protection for principle. Cannot access the funds without paying 10% penalty and pay ordinary income tax on growth/contributions.
The alternative to a Roth is cash value whole life insurance – unlimited contributions and guaranteed growth with principle protection – plus asset protection and liquidity.