Both are VERY loud, obviously. I find macaw screams more tolerable than cockatoo screams personally. Too's have a very high-pitches shrilly scream that gets to me. That's not to say a macaw on full volume isn't LOUD, it's just a different type of loud. Macaws sound like how you'd expect a parrot to sound, cockatoos sound like banshees

Have you tried finding videos of a macaw screaming, turning the volume all the way up, then imagining it about 100X louder, which it would be in real life
Edit: Are you planning on getting a macaw or just curious? Noise is a MAJOR consideration with bigger birds, and I would strongly suggest if you're considering a macaw to listen to some really vocal ones in real life to see if it's something you can deal with. We used to visit a bird store where the owners had their personal macaws (a few B&G's, a HY, and a scarlet, if I remember correctly) always there to 'greet' customers. Even the joyful squawks from that 'welcoming committee' were a bit much

Parrots voices are designed to pierce dose rainforest after all, and in domestic homes and suburban neighborhoods, it's not always a very... welcome personality characteristic:20: The noise of those XL birds is one of the big reasons I would personally not consider owning one. I find the noises my amazon can make MORE than loud enough for me:52: