the highest thermal performance I had had with these newer local air-conditioners is Orient.
When installing please make sure that after connecting the unit, your A/C tech pulls a solid vacuum before opening the valves on the outer unit. There are many goofs out there posing as A/C techs which know nothing at all. Also make sure that the tech adds gas as required if the pipes are longer. It will work nice.
Depending on the placement of the unit and your demands - you may need a more heavy duty unit like a General or Winia with American Bristol Compressor to keep up. (e.g. if you live at the highest floor and have a low(ish) ceiling.