I have TowBoatUS and have been towed 3 times, the first out of my own pocket [emoji32][emoji24]. This prompted me to join. Service all the times was great. I look at my yearly fee as a part of insurance coverage for the boat. When I signed up,  I don't remember Seatow being on the lake. 
I believe that Andrew's Marine Service out of Minge Cove also offered towing service,  but I don't know if he still does. 
To answer your question,  you really need to look at the two major players, Seatow & TowBoatUS, look at their respective coverages & benefits,  their costs,  and what best fits your needs.  
I have compared the two a few years back and did not find a compelling reason to switch. 
Good luck.
Dave
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