Peel Away Marine Strip II
You are correct to be skeptical. They are two different products, with a 5X price difference, caveats on use are different, chemical composition is definitely different. #1 requires application of a thicker coat than does the #6 product although it is so much cheaper it doesn''t matter as much. Cost of the building product version is about $95 for a 5 gallon pail whereas the marine product is about $250 for the same quantity.
I have used both and if money is no object go with the marine product although the #1 product works very well with Pettit''s ACP ablative paint, and quickly too so it might do the same job with any of the ablatives.
I cant speak to the danger of either product inadvertently removing or damaging barrier coats except that I believe the #1 product would be less troublesome.
Somewhat unrelated to your question but perhaps of interest to others using PAW on boats without barrier coats, the last bottom I did I used PAW #1 to remove the existing ablative paint so I could change to a hard bottom paint instead. After removing the ACP-50 with the PAW, I washed the hull down with Pettit''s Hull Wax remover and it did an incredible job. It did just enough of an etch to the gelcoat, a sanding wasn''t required before repainting.