I have a Roth IRA with Vanguard, and I saw this question: What is the difference between shares and ETF? about the differences between Admiral Share funds and ETFs. I've also seen stuff talking about how ETFs are more tax-efficient because when investors move in and out of the fund, those transactions happen in the secondary market and the fund manager doesn't need to buy/sell shares to redeem shares of the fund, which creates capital gains.
So based on that, is there any reason to prefer ETFs to Admiral Shares funds in an IRA? For example Vanguard's healthcare fund, which has an ETF and an Admiral Shares fund. I don't pay commissions when I buy/sell Vanguard ETFs in my Roth IRA, but it's nice to be able to buy in dollar amounts (fractional shares) of a mutual fund, which I can't do with an ETF. I also have enough my account that I won't pay the $20 annual fee they charge for a Roth IRA Brokerage account (which I need to open to be able to trade ETFs).
Anything else I didn't think of? There won't be any tax consequences because it's a Roth right?