The answer to 'best AC' is that the best air conditioner for your home depends on several factors, including the size of your home, your climate, your energy efficiency goals, and your budget. In general, a high-efficiency central air conditioner or ductless mini-split system are often considered the best options for most homes.
Central air conditioners come in a range of sizes and efficiency levels to match the cooling needs of your home. Look for a unit with a high SEER (Seasonal Energy Efficiency Ratio) rating, which indicates how efficiently it uses electricity. Ductless mini-splits are also highly efficient and can provide cooling (and heating) for individual rooms or zones. They're a good choice for homes without existing ductwork. When selecting an AC system, it's important to have a professional perform a load calculation to determine the right size unit for your home.