I know that you've already made your decision but I wanted to throw this out there.
My DH has worked for a Lincoln dealership for over 32 years as a journeyman technician. Even with him knowing how to fix our cars, we always purchase an ESP. The price of parts can be high. I think that he said that there are over 20 computer modules in each vehicle. If one goes out, it can be expensive. That being said, the price of an ESP varies from dealer to dealer.We paid $840 for a 6 year/60,000 Ford Premium Care ESP on a new car. Of course it's really not 6 years/60,000 since it has a new car warranty. This price was $50 over dealer cost. I tell you this just so that people understand that they can negotiate with the finance person on the price of the ESP just like they do with the sales person on the price of the vehicle. He's always said that the finance person is the highest paid person at his store. They make commission on the warranty, fabric protection, outer protection... (we don't purchase those). If you can't find anyone that takes the warranty, the customer has to pay full price. It can also take longer to repair vehicles with after market warranties. Many of these companies require that they send someone from their company out to verify the problem or for the technician to send pictures for someone in their company to review before they will authorize a repair.
Another thing to keep in mind is that many repair places do not accept some after market warranties and if they do, the customer may still end up owing more than the deductible. At his dealership, if a customer doesn't have a Ford ESP, the customer may have to pay the difference between what the warranty company will pay and what the dealer charges. After market warranties can also take longer to repair. Most require that they verify the problem before they authorize the repair. This means that the tech has to take the car apart and leave it sit while they wait for someone from the warranty company to come out and inspect it. Some require that the tech take pictures of the problem and send them to be reviewed.