I carry both AAA RV and Good Sam Road Service. The primary reason is that I travel on the NYS Thruway. They have approved service providers, such as AAA. If you need service, the approved providers are called. I not sure how it works, but I would bet that unapproved providers are not allowed to service vehicles while on the Thruway.
The other reason I carry both, is I figure that it is not that expensive to increase your ability to get service wherever you are.