We have a Frigidaire. It is a 15000 BTU, which is the highest BTU you can get in a 110 volt unit. Not super quiet, but I don’t have a problem with it. Also, Frigidaire is, I believe, good in terms of service.
Please note: it’s important to make sure that you get the correct BTU for the room you are trying to cool. Room dimensions, as well as type of room (dining, bedroom), as well as floor the room is on (heat rises – attics tend to get HOT) all figure in. Don’t buy an air conditioner blindly – you’ll regret it.
I sold a few air conditioners in my time, so boruch HaShem I remember a few points . . .