I read pretty much evenly distributed negativity on both GS and CN. Mostly around response times.
Time to respond is not necessarily a reflection on the ERS club. The towing companies are contracted. They have contracts with others too, not just GS or CN. AAA, various insurance companies, etc. If you hit them on a busy day, you will wait. I don't believe any ERS guarantees specific response times.
My only concern about CN is that they will only tow you to the nearest authorized repair facility. That means if I'm 99 miles from home, and the nearest facility is 5 miles, I have to travel back there to get my vehicle. Both AAA and GS have 100 mile towing to any destination of your choice.
