Before, few years back Voltas is killer in the market. But now the products quality and durability are getting degrading slowly. TATA started using china material and for ex: 5 star means its true value is 3 and EER, BEE and IBU is not bothered much.
Among all Split AC brands the best brands are Carrier, Blue Star and OGeneral. Because many years they are just striving only on one busines and resarch and the products are really good. Any product in the world have minor defects and some rural places may have llittle serivce delay.
Count Hitach models, I if O General is expensive and if you are from City.
Just I want to advice only one thing all these guys LG, Samsung, Onida, godrej, videocon, panasonic, la bla la bla. products they are just make their mark in the business and brand name by using assembly products. All these products life span max is 4 to 5 yrs depending on usage.
I have above these three brands in my office from 12 yrs and zero maintance except very few minor issues like cleaing( Carrier, Blue Star and OGeneral.).