When is it better to fry with oil and when is it better to fry with butter?

I usually see people frying eggs with butter and sometimes with soy oil - for example. But there are a lot of other ocasions in which these two options appear. My guess is that there are kinds of frying, for example: When you want to fry eggs, it's better to do it with butter, this is a kind of lighter frying. But when you are frying chips, it's better to do it with oil, this is a kind of heavy frying in which the food much receive more heat for a long time (I guess that oil can reach temperatures higher than butter).