No! No! No!
The growth in a 401k is tax-deferred, not tax-free! Your higher growth assets (equities) will be in taxable accounts (which can be tax free if you're in the 15% bracket or lower or otherwise 15%) and tax-free accounts like a Roth.
Not at all! Heck, normally I don't bother replying to threads where you already gave my preferred answer. How come we disagree here?
If your tax is 25% into a 401k and 25% out (any rate that is the same in and out) then your growth is tax free. Here's the math:
You make $10,000 that is normally taxable. You have three choices, defer taxes using a 401k, pay taxes and stick it in a Roth, or pay taxes and stick it in a taxable account.
Start: 401K=$10,000; Roth=$7,500 ; Taxable=7,500
Then you let it sit for 10 years and manage to double your money in equities that never generate any taxable income in the mean time.
Growth: 401k=$20,000; Roth=$15,000; Taxable=$15,000
Then you take your money out to spend it, paying your 25% as necessary, and 15% capital gains.
After Taxes: 401k=$15,000; Roth=$15,000; Taxable=$13,875
So in the end the 401k was the same as the Roth, and both did better than the taxable account. Growth is tax-free in a 401k.
Two things will impact this result, changing tax rates (tax rate out is different than tax rate in), and the fact that Roth 401k contribution limits are the same as traditional 401k limits. Obviously if tax rates are changing it will be advantageous to pay at the lower tax rate, in or out of the account. The contribution limits favor the Roth since you can contribute more after-tax value to a Roth if you are contribution limited.
And yes, if you can stay in a 0% CG tax bracket, the taxable account equals the 401k and Roth if you can avoid non-qualified dividends.
Let me see if I can find the thread about 401k growth and asset placement.