If they all track the same index, they should all be virtually the same. High liquidity/volume and low expenses are best.

>as that seems like my best option Will hold long term

Personally, I consider S&P 500 obsolete (in any account where you're not limited to a short list to pick from): why ignore the US extended market and ex-US markets?

Doing S&P 500 only means you take on an uncompensated risk (single country) and ignore a compensated risk (smaller caps). For long term (or even mid-term), I see no reason to do either of those.

>Which has the lowest fee?

Fidelity's FXAIX is the lowest I know at 0.015%. Though I'd consider FSKAX better for the US market: it covers smaller caps as well and is the same cost at 0.015% (then just add FTIHX or similar for ex-US).

>I think fidelity has a zero fee one?

No. Fidelity's Zero funds follow Fidelity designed indexes, so FNILX is 500 large caps and is probably more rules based than S&P 500 is (see the difference in how each handled Tesla in 2020).

Also FXAIX and FNILX (and FSKAX) are index mutual funds, not ETFs.

Edit: Typo

If this is in an IRA, then the Zero funds are great options (I invest in them myself). If this is a taxable account, then you'll want a tax efficient and low cost ETF that is not "substantially identical" to what you hold in IRAs so as to avoid wash sales. Good options are: VTI/VOO, ITOT/IVV and SCHB/SCHX are all good options.

Good points…. This is going to start as a taxable account so o will start with ETFs…. I do also want to look into a fund for my IRA too which I have through Vanguard so I assume I would just use Vanguards index or mutual fund.

Obsolete? It has traditionally delivered a 10%+ return per year for decades.

It's splitting hairs, and the S&P500 has just become a "catch all" term for things like total market.

Fidelity's FZROX has a zero expense ratio. I would only own it though in a retirement account.

But why use that when for the same costs you can use US total market? Better diversification and gives coverage of a compensated risk factor.

The S&P 500 has returned 11.88% since 1957. I think the intent of diversification has stayed the course. 66 years of great returns isn't some fluke.

The biggest risk I'd say, is when you plan to retire. As it is volatile, it takes big swings. Many funds down significant amounts right now would be rough if you are looking to retire. However, historically, it returns.

I'm not saying avoid S&P 500. I'm saying to not use S&P 500 only funds, but to use broader funds that cover S&P 500 and more.

S&P 500 works, but for the same exact cost and difficulty, there are better options (US total market). And for only a slightly higher cost (and maybe 1 additional fund), even better than that (going global).

>However, historically, it returns

Like I said, it has worked so far, but it both:

• Ignores the compensated small cap risk factor

• Takes on the uncompensated single country risk factor

I don't see any reason to do either of these.

What’s the “downside” or con of owning this, or something similar, in a taxable account?

ETFs are better than mutual funds in a taxable account. It gets complicated for why, but its just slightly more tax efficient. Mostly splitting hairs.

Also, FZROX can only be owned through Fidelity, so if you ever wanted to leave Fidelity, you'd have to sell your FZROX and incur a large tax penalty. With a retirement account, this isn't an issue.

ETFs though are portable and can go to any brokerage.