Changing Money: Which airport - departure or destination?

You'll almost always get a better rate in the country you're traveling to, usually much better than in your home country. It also depends on the currency of your home country, major currencies like British Pounds, Euros, US Dollars and some others often get the best rates. In the country where I live, you also get a better rate on large notes (bills).

You also need to compare rates at different banks and currency exchanges, they can vary widely. Airport currency exchanges often give poorer rates compared to banks and exchanges in the cities and away from the airport. Also make sure you don't bring worn or damaged notes, many foreign banks and exchanges will not accept them. Credit cards and ATM's are also good, you usually will get the bank rate which is normally higher than the cash rate, but be careful of foreign ATM fees in some countries.

When i went to France, i took US money and bought euros in France.

I later learmed is when i used my bank card, i saved money on the exchange rate better than changing currency.

So use your bankcard instead of changing cash to save money.

It's not the airport, but the airlines which determine the rates. It's been a while since I flew to Europe, but KLM usually has ok rates.