I have no experience with roadside coverage from Good Sam, so take my info for what it's worth.
IMHO in most places you'll end up with the same tow companies, at least outside big-city areas where there's enough competition to have companies contract with just one.
I'd compare on price and benefits. I already had AAA because I buy my car insurance through them. Remember you have to buy the RV-level (Plus RV or Premier RV) from AAA or they won't tow both your trailer and tow vehicle, at least not as a covered event.
I don't know what Good Sam's insurance rates are like, but for the Airstream I did *NOT* go with AAA for my insurance... and someone backed into my truck & we did a claim the year I bought the Airstream, and the Progressive rate for my car and truck were way worse because I had "recent claim history" (even though it was fully paid by the OTHER party's insurance) so all that's worth figuring out first if you're going to get your roadside and insurance the same place.
Over time I've been pleased with AAA, but I've never had to have service while on a trip w/ the Airstream. They have good prices and convenient service on vehicle batteries and a whole slew of discounts at cooperating businesses. Good Sam has better discounts at campgrounds, it seems.
Zero Gravitas — 2017 Flying Cloud 26U | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill