I think this comes down to what you mean by "equivalent." If you are comparing a contribution of, say, $10k to a Roth to $10k to Traditional, I do not think that those are equivalent situations.
IMHO, the appropriate comparison would be: Contributing $10k to a Traditional vs. contributing $10k*(1-taxrate) to a Roth. As @sergio points out, this comparison makes it clear that your marginal rate when withdrawing vs. your marginal rate when contributing is the important consideration.
What @sergio said for his case is also true in my case: I also fully funded a Roth IRA, even at a higher (i.e., while working) tax rate, due to a desire for tax diversification.
I was paying an effective 25% rate during the 2011-2016 time frame when I contributed to the Roth 401(k). Over those 6 years I contributed around $100,000, meaning I paid $25,000 in taxes I otherwise would not have paid if I elected to participate in the traditional 401(k). At the end of 2020, the Roth 401(k) alone showed a balance of $250,000, meaning $150,000 in growth over the last decade.* That growth along with your contributions are taxed at distribution in a traditional 401(k), yet none of it is taxed at distribution in a Roth 401(k). I just turned 51, so I cannot take a distribution for another 8.5 technically, but using today for example purposes only, compared to a traditional 401(k) I am saving at the very least my 25% tax rate on that $150,000 growth difference, or $37,500 in taxes. Meaning I am already ahead. Now if I was in the 12% tax category (which I don’t envision I will ever be considering my Traditional retirement accounts are already over $1M), that figure is halved, or $18,000 compared to the $25,000 tax paid to date.
However, I have at least 8.5 more years (until 59.5) before I can even touch the Roth 401(k) money, so if it doubles (10% annually has been my experience in my 25 years investing in the stock market), I will be at $500,000, or $400,000 growth. 25% of $400,000 is $100,000.00 (plus the $25,000 already paid = $125,000). Since I will be taking that Roth money out over time, and probably not all at once, I estimate that $100,000 saved is a floor, not a ceiling, on the tax savings.
That said, the tax savings is wholly dependent on each participant’s specific situation (tax rates, amount saved, how much growth risk you are willing to take, and what other investments you have). Sounds like you and OP made the correct decisions for you, and I am happy with the decision I made.
* to the extent that there was an assumption that the tax paid would have gone into a traditional 401(k) -meaning a larger 401(k) investment- I was already maxing out, so sadly the 401(k) company would have gotten the same IRS capped amount from me whether a Roth or a Traditional 401(k). Anything more went to supporting my wife and three kids. Assume the smile face emoji here.