The respective accounts though, would have the same amount of capital put into them. If they're invested the same, the end results would be the same however, 100% of the Roth account would be tax free and 100% of the taxable account.....would be taxable.
To change the perspective a bit....you put $1,000 into a retirement account. You do "your best" to grow that $1,000 into $10,000.
You managed to do just that.
The IRS has no sticks in that fire. If your $1,000 goes to zero, they don't care. YOU do, but they don't. If however, you do managed to grow it to $10,000 you are putting that energy into growing it so that you can still give them "their portion" (even though they took none of the risk). So they took none of the risk yet still get a portion of the winnings.
In the Roth account, you get 100% of the reward.
Side comment: Over my career, I've had umpteen people come to talk with me and ask me "what can I (they) do???" Then the story unfolds....
They might have a pension. The have no debts, they've invested well so today, they have say, a million dollars in their (taxable) 401K and are able to live off their social security & other savings. They don't need their 401K yet, they are now (when this happened) 70 1/2 (which today has moved to 72) and they are REQUIRED to take their RMD (Required Minimum Distribution....which by the way, does not apply to a Roth account)
Anyway, so now, they have to take maybe $40,000 out of their retirement account and are going to get crushed on taxes... and Richard...."how can I avoid that???"
Upshot is they can't unless they might want to give it to a charity but they spent 40 years growing the monster and now it's biting them in the ankle.
Had they done a Roth option when it started, then their taxable impact would have been mitigated and they wouldn't have been talking to me about how to avoid the impact of their RMD.