There are just so many around. It is not just WHAT brand but HOW the oil has been extracted. Look for 1st cold press oil since that would be the purest and tastiest.
It does have an effect where the olives came from but it is a matter of personal taste just like honey, taste differs depending on where the honey was extracted from.
Whatever oil you get, it will be better than veg oil.
The price tag will deffinatley guide you on your purchase.