AAA has an "RV specific plan" too, but I would choose one of the others. Too many variables when you move across state lines and potentially to another AAA club region with different practices on RV services.
As to what is "better", I think it's a crap shoot. They all use the same local services and are at the mercy of them for quality, timeliness, and pricing for extra services. GS and FMCA both contract through Allstate Motor Club, whereas Coach Net uses the services of its parent company, National Motor Club. Their contracts may have slightly different limitations on the services provided, but basically you get what either Allstate MC or National MC provides. I'd buy whichever had the more attractive offer on the day I was buying (promotional deals are common).