For me it has been Toyota and Ford being the best, with Chevy dead last.
Classic example: We bought the 2005 Chevy Trailblazer in Jan. 2005. The wife and I went out of town in Aug. to celebrate our anniversary. Of course Aug in southern Ca can be very hot. The A/C in the Trailblazer quit working while driving around town. On the freeway it would freeze you out.
From reading various forums especially Trailvoy.com I had a pretty good idea that the electric fan clutch was bad. (IIRC, GM had about 4 or 5 different "updated" versions of the fan clutch over the first four model years). I took it to the dealership in San Diego where I bought it from and asked them to check it. They checked the pressures and said the system was properly functioning. I explained to them that it cools ok when it's 70 degrees outside, but NOT when it's in the mid 100's. I had printed out the TSB for the fan clutch and told them it was on the passenger seat of the SUV, maybe take a look? The next day they called me and said they replaced the fan clutch and I could come get it. It did fix the problem. After that at idle on a 100 degrees day it would throw 40 - 45 degree air out the vents, vs the 85 - 90 degrees I was getting previously.
Point is - I had to tell them WHAT the problem was, and HOW to fix it. They weren't going to do anything because as the service manager told me: "You can't expect the a/c to be ice cold around town . . . " I told him my (at the time) 10 year old Ford Aerostar would put out very cold air around town under the same circumstances. That seemed to spur him into action.
I do realize this was 10 years ago. If I had to do it over, I might have just replaced the fan clutch myself, ate the cost and saved myself the aggravation.
There were various other problems with this vehicle that GM NEVER fixed and most of them I ended up fixing myself. One was a vibration at idle. I took it to at least 3 different dealerships. One said they couldn't hear the vibration, one said they "adjusted the exhaust system" and one said they couldn't find the problem. In the end a member on the Trailvoy forum found that the motor mounts would go bad, causing the vibration. By the time I found this out, the vehicle was outside of the warranty period, so I replaced the mounts myself. Problem fixed just in time to sell it!