what area are you in?
no-one is asking for your source of income.. so please leave that aside. Ask any oldschool A/C shop if they use vacuum pump when installilng A/C at home and other bits like wiirng gauge and if they are using chocolate/joinder/terminators for wiring or are they twisting and nitto taping??
these 2 very simple questions can filter your search.
Once you install your equipment properly - It will show its real performance as the manufacturer mentions. I personally installed quite a lot of A/Cs and even work on larger central units here in USA (2 to 10 tons) - same principles but on larger scale - and on that large scale even a little error results in extreme high running cost and repairs.