Need cash when I land, best place in Comoros? Airport or places in the city?
Don't use the airport exchange. It's the worst possible place to get money. The best option is to get cash from a bank in the city. The Comorian franc is pegged to the Euro, so you'll get a good rate if you have Euros. I always bring a good amount of cash with me and exchange it at a bank in Moroni. Don't rely on ATMs; they can be out of order or give a bad rate. Go straight to the bank.
My advice is to avoid the airport exchange counter. They have awful rates. The best place to get cash is to go to a bank in Moroni and exchange your Euros or US dollars for the local currency, the Comorian franc (KMF). The rates are much more favorable. ATMs are a bit of a gamble, and you might get a bad rate, but if you have a card that has no international fees, it might be worth a try. Otherwise, just use the bank.
The airport exchange counters are a complete ripoff. You will get a much better rate at a bank in the city. Your best bet is to take a taxi to your hotel and then find a bank. The Comorian franc (KMF) is pegged to the Euro, so having Euros with you is very helpful. I've had good luck with ATMs at a bank like the Banque de l'Industrie et du Commerce (BIC) in Moroni. But I'd still recommend going to the counter for a large exchange to be safe.
Never use the airport currency exchange. You'll get a terrible rate. Your best bet is to find a bank in the city of Moroni. The ATMs can be unreliable, so it's best to go into a bank branch like the Banque de Développement des Comores. The rates are much better there. You should have Euros with you, as the Comorian franc (KMF) is pegged to the Euro, and it's the easiest currency to exchange. Avoid exchanging with random people on the street.