The tax rate on capital gains is the same as the tax on qualified dividends. It's the timing of the taxation that differs. With dividends you pay tax now, with capital gains you pay when you sell the stock.
Distributing cash via dividend or buyback usually happens when a company has more cash than they can productively use. There are a few advantages of distributing money via dividend instead of buyback:
* With a share buyback, the company is actually making a bad investment if the stock ends up being overpriced. There are plenty of instances of companies buying back shares and then having the share price drop, because companies can't reliably time the market any better than the rest of us.
* Investors receive a tangible reward when a dividend is paid. In theory, you can mimic dividends by periodically selling small portions of a non-dividend stock holding. However, this means that you're subject to fluctuations of the stock market, so your "dividend" sale might be 20% more or less depending on the month. Dividend-paying companies, on the other hand, typically aim to have predictably-increasing dividends.
The predictability of dividends, however, is a negative if you're a company that doesn't want to set aside cash for investors on an ongoing basis, which is the case for many tech companies.