The tax-free nature of growth on a Roth IRA makes it a highly appealing investment account to hold, and a similarly appealing type of account to inherit. All else being equal, it’s clearly better to be the beneficiary of an account that will never be taxed, than one that will be taxed over time.
However, the caveat to leaving a Roth IRA as an asset to inherit is that doing so implicitly means that the original IRA owner will have paid taxes to get money into the account, either through systematic contributions spanning many years, or possibly through a large Roth conversion (or a series of partial Roth conversions over time). Which means the benefit of inheriting a Roth IRA is actually more nuanced – if the IRA owner pays “too much” in taxes to create the Roth, the beneficiary may have been better off to simply inherit a traditional IRA and pay the taxes themselves instead!
In fact, ultimately the decision of whether to bequest a Roth or traditional IRA should be driven by a comparison of the original IRA owner’s marginal tax rate, and the expected marginal tax rate of the beneficiary in the future. If the beneficiary’s tax rates are higher, it’s clearly beneficial for the current IRA owner to go ahead and convert the IRA, paying the taxes now at current rates, and leaving the (high income) beneficiary a tax-free account. However, if the reality is that the beneficiary’s tax rates are actually lower – perhaps because the original IRA owner’s wealth is being spread across multiple beneficiaries, because the beneficiary simply has less income and assets, or maybe just due to the fact that the beneficiary lives in a different state that has a lower tax rate – then the best thing a (higher-income) IRA owner can do is simply to leave a traditional IRA to the beneficiary and let the beneficiary pay the taxes at his/her own lower tax rates!