Before sifting through the investment universe for the most appropriate tool for the job, investors should be able to answer one central question: What is my investment thesis? For long-term core positions, there's a good chance that investors can get the exposure they seek through exchange-traded funds. However, when thinking about shorter-term tactical bets (or satellite positions), the line gets blurred. Usually, the decision boils down to which ETF is the best tool for the job. At other times, the right tool might not be an ETF at all but, rather, a stock. Regardless, the key is to match the thesis with the investment vehicle that most closely correlates with your conclusion.