There are lots of factors that determine whether an auto service plan company is a great one or not. And unsurprisingly, the most important factor is the quality of the plans themselves.
Firstly, you want to take a look at the comprehensiveness. Do they have several packages you can't choose from to suit particular scenarios? Exactly how comfortable are these plans? Do they let you pay monthly car repairs! If you're comfortable with these, you may move on to flexibility.
By flexibility, I mean the range of garages and auto repair services they support. Do they let you choose your own garages, or do they force you to use certain ones? All of these matters.
Afterward, you can then consider the experience (go with a company that has been in the game for more than ten years, and that is customer-focused), price transparency, quality control, technician qualification, professionalism, and customer service.