Tax-wise in the past, it has been better to keep tax-efficient equities in taxable and tax-inefficient fixed income in tax-advantaged. So I think they have things backwards.
Things may have changed now that bond funds pay so little and equity funds often have yields higher than bond funds. Thus some folks recommend keeping the same asset allocation (at least stocks:bonds ratio) in both taxable and tax-advantaged accounts.
Advantages of equities in taxable:
- Equities are volatile, so there are generally more tax-saving tax-loss harvesting opportunities if they are held in a taxable account.
- Unrealized capital gains are not taxed.
- Realized long-term cap gains are taxed at favorable rates as low as 0%.
- Equities get a stepped up basis for heirs if you die.
- Losses offset gains and excess losses are deductible on your tax return.
- Qualified dividends are taxed at favorables rates as low as 0%.
- You get a credit for foreign taxes paid.
Disadvantages of non-tax-exempt bonds in taxable:
- You pay taxes on your bond dividends at your marginal income tax rate.
But with interest rates turned upside-down nowadays and tax-exempt munis paying more than CDs and Treasuries, perhaps bonds in taxable is the way to go for new money. If bond funds lose money, then tax-loss harvest. If things change so that bonds are paying a higher yield, then the share prices of bond funds will drop and allow one to sell at a loss and go back to the old way of bonds in tax-deferred.
Of course, one might say "Put things that stand to gain the most in a Roth IRA", but even that has problems. The things that are possibly going to gain the most are also the things that are going to lose the most. A Roth is precious future tax-free space, so you don't want to lose money in it if you can help it.
We write about Roth conversions all the time on this forum. With a heavy dose of stock funds in taxable, one can use those funds for expenses and pay hardly any taxes at all which in turn allows one to do Roth conversions and pay hardly any taxes at all.
So our taxes have been relatively low because we have been doing equities in taxable and keeping bonds in tax-deferred. On our Schedule B we have essentially no interest income, no taxable bond income, and mostly qualified dividends. With our bond allocation in tax-deferred our IRAs have not become enormous, but that also means our future RMDs (if any) will not be enormous and our conversions to Roth will be manageable.
I think the MME advice would cost us an extra $10K to $20K more a year in taxes.