so far as per experience
samsung - madali masira (we have more than 5 units of split type inverter and almost all dumaan na sa sira of some sort) units are around 5 yrs old
lg - mas matibay sa samsung from the looks of it but medyo mas maselan ayusin (for one thing, no error codes, no manual switch - actually meron pero hindi nakalagay sa guide sinabi lang ng nag install). around 3 yrs old ang unit and nagkaron ng slight hitches like hindi gumana ang remote (due to nabasa yung wire kasi dumikit sa copper tube - kasalanan nung naglinis), humina ang lamig (due to power fluctuations - kaso ilang visit ang ginawa before naconclude na power fluctuations since again no error codes so need actual na observe ng technician to see the problem)
panasonic - great support, so far wala pang problem ang unit