If you take a non-deductible contribution to a traditional IRA and roll it over to a Roth IRA, you get the normal benefits of a Roth IRA. This is often called a Backdoor Roth IRA.
It may help you to know that if your tax rate is the same at both contribution and withdrawal, traditional and Roth IRAs have the same benefit. Take $1000. Pay any tax (say 25%) for the Roth. Invest in something that quadruples. Withdraw the whole amount after retirement. Pay tax (still 25% or whatever) on the traditional. You end up with the same amount.
The Roth starts with $1000 less $250 taxes = $750. Amount quadruples to $3000, and is tax-free upon withdrawal.
The traditional starts with $1000. Amount quadruples to $4000. Withdraw it all and pay $1000 (25%) in taxes. $3000 left.
The Roth gives less benefits if the tax rate you pay in retirement is lower than the tax rate you pay now. It could conceivably give more benefits if your tax rate after retirement would be higher, but most people won't make more money in retirement than they do now. Perhaps taxes will increase, as revenue is currently lower than spending.
You can actually contribute more with the Roth IRA. This is be cause if you start with (e.g.) $6400, pay $1600 in taxes, and then contribute $4800 to the Roth IRA, that is the equivalent of a $6400 contribution to a traditional. But you can't make a $6400 contribution to a traditional; you are limited to $5500. So a Roth IRA's $5500 limit is the equivalent of a $6875 limit for a traditional.
Non-deductible contributions to a traditional IRA still get tax deferral on earnings. So you don't have to pay tax on capital gains and dividends until you withdraw.
Even if you get no special tax treatment, traditional IRAs receive protection in bankruptcy.
If you retire early, you can convert traditional IRA funds to Roth IRA funds and take the income before you get Social Security. So you might find your rate lower. This also may help you bridge the years between 62 (when you can first take Social Security) and full retirement age (when you get the maximum benefit from Social Security).