My only trouble with ETFs is you cannot buy and even amount like $200 each purchase. It has to be a multiple of the share price.
The good thing about mutual funds is you can buy fractional shares, so the same dollar amount will buy a different number of shares as the price changes. It is easier to dollar cost average that way.
Now if one reinvests dividends on ETFs, I think that can buy fractional shares. But I am not sure all allow dividend reinvestment.