We've had Good Sam ERS since 1996. Only used it once and they were there quickly. So they are way ahead in terms of service provided vs $$$ invested by me. Howeverwe travel 400 miles accross central Nevada every year on Highways with names like Extraterestial Highway near Area 51. That sometimes putsus about 200-250 miles from the nearest RV or Dodge diesel repair facility. The piece of mind of having an ERS that will handle your emergency no matter how far you need to be towed is worth it. They alsoare familiar with what kind of rig to send to you depending on your rig and type of emergency. I'm not so sure about other auto type insurances. I had one bad experience with an auto insurance company that didn't end well whenI blew a transmission years ago while towing a TT. Since thenI have had the Good Sam ERS.
I have also heard good things about coachnet. Seems they provide the same service, with the same providers, for a few $$$ less.