Open Ended Mutual Funds determine their price per share at the end of the day's trading. They calculate this Net Asset Value (NAV) by looking at all of their holdings and dividing by the number of shares. They allow purchases and sales using this NAV calculation. (Note, this requires that they keep a little bit of that NAV set aside in cash so that they can pay out if there are more shares being sold on that day vs buy. They can also limit or adjust sale prices in certain circumstances, e.g. if they had a huge influx of sell orders that day, they could insist that the following day price be used to allow them to sell assets.)
ETF's (Exchange Traded Funds) are like a mutual fund in that they own underlying assets. Some ETF's are very broad based, for example the SPY ETF reflects that (mostly) largest 500 public companies in the United States (in terms of market cap). Some are much more narrow, e.g. GLD is an ETF that owns...GOLD. Since they trade (like a stock), it is possible that that asset value of the underlying securities DIFFERS from the price that the ETF is selling for. This is expressed as a premium or discount to underlying NAV. However, this typically isn't an issue for large ETF's that are actively traded, because there are mechanisms where new shares can be created or removed which acts to keep the tracking error small. (For instance, there is a procedure by which SPY shares can be 'created' by supplying the underlying shares of the 500 companies in the SP 500 index).
So, ETF's have the advantage that they can be purchased during trading and you would get that price as of that moment (as compared to end of day pricing only). ETA: So, ETF's have the disadvantage in that they can be easily traded - don't do this.
You should also be comparing fees associated with mutual funds and ETF's. While one might think that ETF fees would be higher, this is not necessarily the case. For instance, SPY's gross expense ratio is 0.0945%.
Here's an example of information:
https://us.spdrs.com/en/etf/spdr-sp...8GqbJ86Eh1NMPQy8moY2tPpVW6kIqkshoCsZ0QAvD_BwE
From a personnel perspective, I have both mutual funds and ETF's. Mostly mutual funds in my 401(k)/457(b), but I use ETF's in my IRA/taxable account. (For that matter I have individual equities).
What you should be looking at is your overall strategy: What your asset allocation is, what your risk tolerance is. Whether something should be invested in a particular mutual fund or ETF comes AFTER understanding your investment strategy.
Hope this helps, and feel free to ask questions.
