DCF Firm vs Equity methods

Hi,

In what situations would one need to valuate companies based on the Free cash flow to firm (FCFF) vs the Free Cash flow to equity method. It would seem to me that firms buying out other firms value the entire company (equity + debt) while investors must look at the equity valuation? However, don't individual investors looking at whether a firm is trading at undervalued prices or not need to compute DCF based on the firm method?

Any clarification appreciated.

Thanks