I think one thing that must be pointed out is that not all ERS services are created for the same thing. Some exclude trailers unless you have the premium plan. Some require that the trailer be a travel type trailer and will not cover utility trailers. Some probably exclude motorhomes. Some have milage restrictions while others don't. What is best for me may not be best for you. It is necessary to read the accessable portions of the plans to find out if they will work for you. As with everything in the market place today, "Let the Buyer Beware!" And you have more choices that just Good Sam, Coach-Net, or AAA. There are others out there.
Edit: Your tow service through your auto/RV insurance policy may be for towing from accidents only. And some auto insurance companies offer optional regular ERS coverage for breakdowns. You need to know which you have. You might think you are covered for a breakdown, and not be!