Good Sam, AAA, CoachNet and others offered by insurance contract with providers to give assistance on the highways and biways. The service will be as good or as bad as the contracted provider. AAA as independent regions, if you need RV coverage in the wrong region you may be asked to pay up front and apply for "reasonable reimbursement." AAA will tow you of the road to a safe location, and then has up to 3 hours to re-tow you to a repair facility. (Happened to my family, since the re-tow was after 5pm on a Saturday to a small town, we lost a full day waiting for the shop to open Monday.) There are plenty of threads on this site regarding problems with Good Sam and CoachNet. Personally I have used Good Sam twice and have been pleased. I previously used CoachNet once and felt abandoned on a major highway. I just renewed my Good Sam for three years and received a discounted price. Good Sam does cover any car you are driving, just like AAA you must be present to use the service. Hope this helps your decision process.
Happy Trails.