Which one do you prefer – etf or an equivalent index fund?

I have been reading about differences between the two. These are the two differences :
1) ETF does not need a minimum to start with.
2) ETF is traded like stock- buy and sell multiple times in a day. Index fund is traded once per day.
3) you can automatically re invest dividends from index funds

But these three differences do not seem too big of a difference to prefer one over the other.

So what am I missing? Why would you prefer one over the other?