Looking at a split as an independent event is completely missing the point. The split is not only a one-time transaction, it is a powerful progression in value. Splits make shareholders feel great and engender in them a sense of greater wealth with little expense to the company. Nothing but good will endowed to the shareholders. A stock buyback is a sign of corporate financial health.
Buybacks increase earnings and the value of shares.
The number of shares outstanding are reduced which increases share price as well as earnings. Stock buybacks anticipate higher share prices which usually means corporate owners and managers, the ultimate insiders, expect share prices to go up. Buybacks cuts your taxes. Buyback stocks can act as a safety net. A company holding large numbers of its own shares has a strong incentive to purchase more shares when prices decline.