My accountant sent this info to consider.
The first major advantage is that you completely avoid paying capital gains tax because you are donating the stock itself rather than selling it, so the gain is never realized. A second benefit is that you still receive a charitable deduction based on the full fair market value of the stock, not what you originally paid, which creates a powerful double effect of avoiding tax while also reducing taxable income. A third advantage is that if you use a donor-advised fund, you can take the tax deduction in the current year while deciding which charities to support over time, giving you flexibility in how and when you give.
On the downside, the most important drawback is that once you donate the stock, the money is permanently gone and no longer part of your financial assets, which removes any future flexibility. Another issue is that you may be giving up a potentially better tax outcome for your heirs, since holding the stock until death would allow them to receive a step-up in basis and avoid capital gains tax anyway. The final drawback is that this strategy does not improve your cash flow at all, since it reduces taxes but does not generate any actual liquidity, which can be a problem if you still need access to cash for expenses or obligations.