The belief that bigger is better does not apply to choosing an air conditioner. Most can see how an air conditioner that is too small will provide inadequate cooling and comfort. An air conditioner that is too small will be working overtime to keep the house cool and will use more energy in doing so.
An air conditioner that is too large will cool the home quickly, but it will shut off before it properly dehumidifies the air. If your air conditioner is too large, the house will be too cold or too humid for comfort.
Your best bet is to purchase and install an air conditioner that is properly sized for your home. Your air conditioning contractor should always come to your home to take measurements and consider other factors such as window placement, insulation, etc. to determine the appropriate sized equipment.
All Year Cooling will provide a tentative estimate over the phone, we are one of the only South Florida contractors who do this, as well as a written estimate once we come to your home to take our measurements.