Thousands of Americans will receive a lump of coal for the holidays: a layoff notice from an employer trying to polish the books by year-end.

Among the many choices facing those who lose a job, move to a new firm or retire: keep the old 401(k), shift to a new employer’s, cash out or roll into an IRA? There are a couple of subtle ways to determine which option is best for you.

First, does the old plan give you access to “institutional class” mutual funds that carry especially low fees? For individual accounts, these shares are generally reserved for investors with large balances, often $100,000 or more. Shifting your money from the 401(k) to an IRA might be less appealing if investing in the same fund would require downgrading to “investor” shares with a higher expense ratio.

The Vanguard 500 Fund investor-class shares (Stock Quote: VFINX) charge 0.16%, for instance, while the “admiral” class of the same fund charges half as much. The admiral shares (Stock Quote: VFIAX) have a $100,000 minimum account balance for individuals.

Don’t just assume the 401(k) offers a cheaper class. Some 401(k)s offer only the more expensive investor shares, even for people who have enough in the account to meet the minimums for cheaper ones. Those investors would do well to roll over to an IRA to get the less-expensive shares, assuming they want to stay in the same funds.

The second issue: could you reduce expenses by moving from a mutual fund in a 401(k) to an exchange-traded fund in an IRA? ETFs are not common in 401(k)s, but they can be preferable because of lower expenses.

The SPDRs ETF (Stock Quote: SPY), for example, tracks the Standard & Poor’s 500, just like the Vanguard 500 fund, but has a 0.09% expense ratio. Since it is traded like a stock, there is no account minimum. That would make this ETF better than the Vanguard fund if you did not meet the $100,000 minimum for the fund’s admiral shares. To invest in the ETF, you could roll your 401(k) into an IRA with a discount brokerage such as Charles Schwab (Stock Quote: SCHW) or E*Trade (Stock Quote: ETFC).

Third, does your 401(k) have a brokerage option, which would let you invest in just about anything? If it does, you could stick with the 401(k) without facing any limitations. Find out what you’ll be charged on commissions, especially if you expect to conduct lots of trades.

Of course, there’s no point to sticking with a former employer’s 401(k) if you don’t like the investment choices. Shifting your money from the former employer’s plan to the new employer’s can offer convenience, as you’ll have only one account to track. But it makes sense only if the new firm’s plan has some special feature you could not get with the old plan or an IRA, such as access to investor-class shares with low expenses.

For many 401(k) participants, rolling over to an IRA is likely to be the best option, since it offers far more investing choices and, in many cases, the chance to reduce fees. Also, you can continue to put new money into an IRA, while you generally cannot continue contributing to a 401(k) kept with a former employer.

The fourth option, cashing out of the 401(k), is often a bad choice. Withdrawals are subject to tax, as well as a 10% penalty if the investor is under 59 ½.

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