Final answer:
The most relevant tax credit for investment decisions is the dividend tax credit, which alleviates double taxation on dividends, thereby affecting investment returns.
Step-by-step explanation:
For decision-making purposes from an investment perspective, the dividend tax credit would generally be the most relevant tax credit. The dividend tax credit is designed to encourage investment by reducing double taxation on income earned by corporations and then distributed to shareholders as dividends. Understanding how this credit can affect the after-tax return on an investment is crucial for investment planning. In contrast, credits like the spouse or equivalent to spouse credit and the basic personal credit mainly benefit individual taxpayers based on their personal status and are less directly related to investment decisions. The pension tax credit could be relevant for those with pension income, but it is specifically tailored towards income from pensions, rather than broader investment income.