If you want durability I will suggest panasonic, my parents room has a Panasonic ac. Working fine since a decade, no gas leakage no gas refill till date. While our guest room has carrier ac which empties gas in every 2-3 years, cooling is much worse.
@Kushagra_ You are right, a technician also told us the same but its industry wide, when we thought about switching our old Panasonic ac.
PS - he told us older ac had good compressors, newer backdoor units are shite.
@Anupama_Jha We have 2 General window airconditioners at one of our offices and they are probably 30 years old. They work better than many new generation units. I don't know about how economical they are but they cool wonderfully in the Bombay summers by the sea.