You'll find two that get the most mention: Good Sams and the other is Coachnet. The service that you get at any one place is totally dependent on who the ERS contracted with in that area. Some local tow service. The ERS do not own any tow trucks. So if the local tow guy is good then you'll get good service, if he isn't you won't.
I have had both and use Coachnet right now, but check the prices and what services they offer and decide based on that. A note on AAA, in some places they offer RV towing and in others they don't and often their RV towing is limited by their terms. And be sure to determine if you are out of their area that you will or won't be fully covered. Some people also use their Insurance companies service, I can't comment on those.