I've seen many people favor FXAIX over VOO because of its slightly lower expense ratio (and they don't care about intraday trades or options). What they don't realize is that any savings from the lower fee will be more than offset by the capital gains taxes incurred by holding a mutual fund in a taxable account. For example, on a $1 million investment held over 30 years, FXAIX may save about $40k in expenses, but any benefit is lost after the $120k–$180k in capital gains taxes... which is not something you'll have to worry about with VOO