Many people think more BTU"s will cool better, but you need to be carefull and size the AC to the sq. footage.
13,500 BTU 400 sq. ft min. 500 sq ft max.
"Do not buy an air conditioner which is oversized (too many BTUh) for the area you need to cool. You may think that bigger is better, but not in the case of air conditioning.
To make a room comfortable the air conditioner needs to both cool the room air AND dehumidify the room air.
If the air conditioner is too large for the space to be cooled, the temperature will drop quickly and the A/C unit will shut off before the air has become adequately dry.
The room will be either too cold or too humid for comfort."