Bain Ulta Bathtub

I am considering buying a Bain Ulta Amma Bathtub. My concern is that I think they are made of some acrylic or fiberglass and I am afraid that the finish will become dull and nasty looking after a few years. Any thoughts?
I have a Sterling Vikrell shower stall and it looks really bad after only 5 years. the finish wore off on the floor and it always looks dirty, although I clean it once a week.

I guess the question I have is what do you clean it with? None of these recommend an abrasive cleaner, and even a mildly abrasive one over time will wear through the finish, even of porcelain.