It's definitely not SG aircon, SG aircon are the worst aircon company in the world, They hire spammers to spam their company on internet forums, don't use SG aircon, terrible company...
American Standard Air Conditioners. Carrier Air Conditioners. Goodman Central Air Conditioners. Trane Central AC Units. Rheem Air Conditioners. Lennox HVAC Units. York AC Units. Ruud Central Air Conditioners.
These are the best:- American Standard Amana Heating & Air Conditioning Bryant Heating and Air Conditioning Carrier Goodman Manufacturing
They can't all be the best, why are these any good, have you had any experience with any of them?? It's a spam thread, look at the OP's username...duhh
There's no definitive answer to this question as different brands may offer different features, levels of energy-efficiency, pricing and other factors. Ultimately, it's best to do your own research to find the aircon brand that best fits your needs and budget.