Is there an advantage to holding an index fund rather than simply having the flexibility of buying and selling with an indexed ETF?

bump...?

Typically smaller tracking error (especially vs smaller ETFs which have to resort to shortcuts in their index replication strategies), and depending on your broker and the funds you're buying you can trade them for free (and of course with no slippage), which is amazing if you're doing EOD swing trading.

TDA for example will let you trade ProFunds and Rydex funds at no cost and with no early redemption fee.