This is a constant subject that comes up over on the mainstream RV forums. The anecdotal evidence is all over the place. For every post saying "It was wonderful", there's another post saying "They wouldn't do a damn thing for me. What a ripoff!"
The reality, of course, is that NONE of these services own their own tow trucks and hire their own drivers. They have to find existing tow companies willing to contract with them and accept their rates.
In some places, there may be a lot of such companies, it's highly competitive, and they can pick and choose which one(s) they want to contract with.
In other places, there may be few towing companies and the good one's already have all the business they can handle, and they don't really want to bother being under contract to one of these services.
Depending on where you have your breakdown, you may get wonderful service or you may get horrible service. There's no way to guess in advance which is going to happen.
As far as AAA, Good Sam, Coachnet, etc. vs State Farm, Allstate, etc. - which reimburse you after the fact and leave it up to you to find your own tow . . .
If you're in some strange, new area, you won't have a clue who to call or whether, in fact, they are any good. You're probably better off calling AAA or Good Sam and HOPING they've got a good one under contract there.
On the other hand, it sounds like the add on for State Farm, etc. is so cheap, you might as well carry that too, as a back up plan, in case AAA or Good Sam CAN'T help you out in that area.
It's always a good idea to have a Plan B . . .
Fortunately, unlike the people driving cars, you've got your house, your bed, your kitchen, etc. right there with you, and you can just settle down and spend the night if you have to, while waiting for things to sort themselves out.
Regards
John