I purchased a full coverage one from my dealer. it was an Alley warranty. I got this one for my 2015 Sonic RS and had great luck with it. The only time I had a problem is when the dealer put through the wrong code for a coolant reservoir, called up Alley and they took care of it right away.
I bought a different one for my wives '18 Trax (through the dealer, who claimed it was a GM certified aftermarket warranty) and they didn't want to do anything when I went to make my one and only claim on it. Even though it wasn't a covered part GM issued a bulletin saying it was a defective part and that if anyone had the issue to replace it with a newly designed one. The part was causing moisture build up and then causing the turbo to deactivate, a 1.4L engine without a turbo becomes a dog while driving on the highway and the turbo kicks off :/ Needless to say we ended up paying out of pocket, though no issues since!
p.s. got a 7yr 85k mile on my '25 Canyon AT4 for $3.5k
Edit: For formatting to make it easier to read, and also to add that others posted as I was and realize now that I may have over paid :/
2nd edit: I see now others posted way before me but for some reason I didn't see them, as you can see I am new here
