With the introduction of the mesmerizing Quinton tub from Signature Hardware in my master bathroom, I had a lot of questions of "why"? And "what makes resin tubs better than acrylic tubs" because the price difference is noteworthy. Let me share with you what I have learned from my personal experience.
(Isn't she a beauty?)
For my professional projects I usually specify resin freestanding tubs. Made to mimic stone, its non porous matte white finish, heft, and the sculptural lines that can be achieved with the material look and feel really good. Its not inexpensive, but a good value for the cost. I specify from Signature Hardware all the time for these (see examples from previous installs).
Besides resin for freestanding tubs, there is also cast iron and copper as luxury options. Metal retains heat very well and copper is a scarcer material so these tubs are on the higher end of the market. They are also very heavy options. I don't have experience with marble or concrete freestanding tubs. They are gorgeous to look at but heavier still and as porous materials I can see maintenance becoming an ongoing issue. And what about acrylic you ask?
I have used acrylic tubs as drop in and undermount tubs and they work just fine for that application. They look a lot like resin, are lightweight and easy to install. They are on the affordable spectrum of the price scale before getting into cheap fiberglass territory. When the acrylic tubs are surrounded by walls and tiles, they actually do retain heat pretty well and are terrific options for a secondary bathroom. And here is where I took a misstep with my own main bathroom.
When we were doing our first round of rush remodeling to get into our house, the budget was tight and I succumbed to the siren song of an acrylic freestanding tub. It was 1/3 the cost of a resin tub and I thought it looked good from the online photos. When it was delivered, my heart sank. It felt bulbous and flimsy. This was my tub?? We went ahead with the install and I lived with it for a few years. I will tell you it looked good for photos but was actually a piece of rubbish and a total waste of money all told. Every time I stepped in, it felt wobbly and like it was going to fall over it was that light. The water would lose most of its heat after 20-30 minutes. After installing so many beautiful tubs in client homes, I couldn't bare to look at it any more and thankfully swapped out for a much better tub.
Bath time is now joyous. Please learn from my mistakes and stay clear of acrylic tubs for a freestanding application. They are totally fine for a drop in or undermount alcove situation. If you want to go a bit higher end, may I suggest a cast iron undermount tub? Surrounded with tile or stone, it is pure luxury (like in the install below).
I hope this little overview helped you when deciding what tub material to commit to on your bathroom design.