Small world. Breakfast with another boat-friends couple this am, and we were discussing this same video.
We would likely go with coated steel
or what all of us have in our boats,
aluminum.
I do have one custom water tank, by a local guy who is an expert in "hot air welding" plastic. I would not want to
completely trust it for fuel, tho. (Just an uneducated opinion...) My main (38 gallo) fresh water tank is welded SS.
Altogether, I have an example of just about every tank material commonly used. Holding tank is rotomolded plastic, fuel is aluminum, one water tank is welded plastic and one water tank is SS.
I guess we are an ecumenical sort of vessel!