In split ACs, the system is not closed. Condenser is separate and evaporator is separate. When AC comes from factory, the outdoor unit is filled with gas and it is sealed. However when you connect indoor unit with outdoor unit using pipes, air and moisture is introduced in to the system. This adulterates the refrigerant, reducing efficiency as well as reduced components life and early failure. Once pipes are connected, the service valve is connected with vacuum pump, it pulls all the air as well as moisture. The second important thing you get to know by vacuuming is leakage, when AC is vacuumed for half hour. Then after another half hour or so, technician observes the guage and see if vacuum holds. If doesn't hold, then there is leakage in system which needs to be fixed before you can release the gas. After this, gas is released in to the system.
In Pakistan Usually, technicians purge the system and they still defend this 30 year old method taught to them by their ustad g's. When someone tells you no need to vacuum and purging is fine, Just ask them if you purge:
How do you make sure all air and moisture is removed?
How do you know how much refrigerant escaped the system causing the system to become undercharged?
How do you confirm there is no leakage?
Lastly, show them the user manual, it is written in bold to vacuum the system with a vacuum pump. Many techs just vacuum with a fridge compressor which doesn't pull much vacuum.
Regarding Acs: Consider Dawlance as well, they are giving 12 years and dawlance was acquired last year by a large turkish electic home appliances company.
Gree has mixed reviews but they are certainly overpriced, not worth the money.
Haier is crap.
Kenwood new models have good reviews.
If you have budget, go for samsung AR5500. Lg/panasonic also good options.
Whatever you buy, try to go for anti rust coating (gold fin in case of orient) and low voltage startup and vacuuming. In my area, voltage in peak summer drops to 185v and LVS is an amazing feature. If you are in Lahore, i can share a contact of technician. He used to work with daikin.
Look at online sites as well as dealers so that you get the best price, orient has their online site and they were giving discounts last month.