The Samsung AR4500 is the entry level inverter , it is B-rated in terms of energy efficiency however it is still a energy efficient and quiet unit which has a 1 year comprehensive, 10 year compressor warranty.
The Samsung AR6500 & AR8500 are the superior Windfree Inverter model which has a windfree mode that disperses the air through tiny microholes within the indoor unit. It allows for faster cooling and quieter operation while ensuring your comfort. It is also A rated in terms of energy efficiency. The main difference between the AR6500 & AR8500 is that the AR8500 has WiFi functionality and a Tri-Care filter whereas the AR6500 does not.
All of the units above will work really well in residential settings , it just depends on client preference/budget regarding which is the optimal choice for you.