It depends on what other funds you have. If your RMD is not enough to cover your tax bill, where else might you get the money to cover the taxes, if not by withdrawing even more from the IRA?
Assuming you have other sources of funds (such as savings account, broker account that is not in an IRA, compensation from working), then which funds you spend first is kind of complicated and depends on your long term goals, your family situation, and other factors. A withdrawal from a traditional pre-tax IRA will be fully taxable. Cashing in other investments might be partially taxable, or even create a deductible loss, depending on your investment performance. This all can have implications for the future, such as leaving assets to your family, or should you ever need long term medical care.
You might want to talk to a financial planner.
