The answer comes down to what you expect the future tax rate to be. If that tax rate is the same (25℅ marginal here), then it is a wash. Yes you will pay more taxes when you pull the money out with a traditional, but it is the same fraction of the original contribution as when you pay the tax now to convert to Roth (all you did was invest uncle Sam's money well).
So if you expect to pay higher tax rate on retirement then a ROTH could be beneficial. Also a ROTH does not have a required minimum distribution (but Congress can change that and it has been proposed).
The argument for leaving the money in the traditional is that you expect a lower tax rate on retirement. Or you don't trust that a future Congress won't decide to add a "nominal" tax to ROTH distributions.
Now if there is a year where your tax rate is very low, then a partial conversion may well be worth it. Also if you your balance is insufficient for a good portfolio and future contributions will be to a ROTH due to income limits, then that would also be a very good reason to convert.